diff --git a/Makefile b/Makefile
index 2271abebf..f18dcb392 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,7 @@ GOTOOLS = \
 					github.com/mitchellh/gox \
 					github.com/tcnksm/ghr \
 					github.com/Masterminds/glide \
+					github.com/alecthomas/gometalinter
 
 PACKAGES=$(shell go list ./... | grep -v '/vendor/')
 BUILD_TAGS?=tendermint
@@ -25,6 +26,8 @@ dist:
 	@BUILD_TAGS='$(BUILD_TAGS)' sh -c "'$(CURDIR)/scripts/dist.sh'"
 
 test:
+	@echo "--> Running linter"
+	@make metalinter_test
 	@echo "--> Running go test"
 	@go test $(PACKAGES)
 
@@ -76,11 +79,40 @@ tools:
 
 ensure_tools:
 	go get $(GOTOOLS)
+	@gometalinter --install
 
 ### Formatting, linting, and vetting
 
-megacheck:
-	@for pkg in ${PACKAGES}; do megacheck "$$pkg"; done
-
+metalinter: 
+	@gometalinter --vendor --deadline=600s --enable-all --disable=lll ./...
+
+metalinter_test: 
+	@gometalinter --vendor --deadline=600s --disable-all  \
+		--enable=deadcode \
+		--enable=gas \
+	 	--enable=misspell \
+		--enable=safesql \
+		./...
+
+		#--enable=maligned \
+		#--enable=dupl \
+		#--enable=errcheck \
+		#--enable=goconst \
+		#--enable=gocyclo \
+		#--enable=goimports \
+		#--enable=golint \ <== comments on anything exported
+		#--enable=gosimple \
+		#--enable=gotype \
+	 	#--enable=ineffassign \
+	   	#--enable=interfacer \
+	   	#--enable=megacheck \
+	   	#--enable=staticcheck \
+	   	#--enable=structcheck \
+	   	#--enable=unconvert \
+	   	#--enable=unparam \
+		#--enable=unused \
+	   	#--enable=varcheck \
+		#--enable=vet \
+		#--enable=vetshadow \
 
 .PHONY: install build build_race dist test test_race test_integrations test100 draw_deps list_deps get_deps get_vendor_deps update_deps revision tools
diff --git a/benchmarks/codec_test.go b/benchmarks/codec_test.go
index 7162e63d0..3650d281e 100644
--- a/benchmarks/codec_test.go
+++ b/benchmarks/codec_test.go
@@ -4,9 +4,9 @@ import (
 	"testing"
 
 	"github.com/tendermint/go-crypto"
-	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/go-wire"
 	proto "github.com/tendermint/tendermint/benchmarks/proto"
+	"github.com/tendermint/tendermint/p2p"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 )
 
diff --git a/benchmarks/os_test.go b/benchmarks/os_test.go
index 9c8fae656..dfadc3128 100644
--- a/benchmarks/os_test.go
+++ b/benchmarks/os_test.go
@@ -18,12 +18,16 @@ func BenchmarkFileWrite(b *testing.B) {
 	b.StartTimer()
 
 	for i := 0; i < b.N; i++ {
-		file.Write([]byte(testString))
+		_, err := file.Write([]byte(testString))
+		if err != nil {
+			b.Error(err)
+		}
 	}
 
-	file.Close()
-	err = os.Remove("benchmark_file_write.out")
-	if err != nil {
+	if err := file.Close(); err != nil {
+		b.Error(err)
+	}
+	if err := os.Remove("benchmark_file_write.out"); err != nil {
 		b.Error(err)
 	}
 }
diff --git a/benchmarks/proto/test.pb.go b/benchmarks/proto/test.pb.go
index 6539cae32..dc21a2a82 100644
--- a/benchmarks/proto/test.pb.go
+++ b/benchmarks/proto/test.pb.go
@@ -24,9 +24,6 @@ import bytes "bytes"
 
 import strings "strings"
 import github_com_gogo_protobuf_proto "github.com/gogo/protobuf/proto"
-import sort "sort"
-import strconv "strconv"
-import reflect "reflect"
 
 import io "io"
 
@@ -392,31 +389,6 @@ func (this *PubKeyEd25519) GoString() string {
 	s = append(s, "}")
 	return strings.Join(s, "")
 }
-func valueToGoStringTest(v interface{}, typ string) string {
-	rv := reflect.ValueOf(v)
-	if rv.IsNil() {
-		return "nil"
-	}
-	pv := reflect.Indirect(rv).Interface()
-	return fmt.Sprintf("func(v %v) *%v { return &v } ( %#v )", typ, typ, pv)
-}
-func extensionToGoStringTest(e map[int32]github_com_gogo_protobuf_proto.Extension) string {
-	if e == nil {
-		return "nil"
-	}
-	s := "map[int32]proto.Extension{"
-	keys := make([]int, 0, len(e))
-	for k := range e {
-		keys = append(keys, int(k))
-	}
-	sort.Ints(keys)
-	ss := []string{}
-	for _, k := range keys {
-		ss = append(ss, strconv.Itoa(k)+": "+e[int32(k)].GoString())
-	}
-	s += strings.Join(ss, ",") + "}"
-	return s
-}
 func (m *ResultStatus) Marshal() (data []byte, err error) {
 	size := m.Size()
 	data = make([]byte, size)
@@ -586,24 +558,6 @@ func (m *PubKeyEd25519) MarshalTo(data []byte) (int, error) {
 	return i, nil
 }
 
-func encodeFixed64Test(data []byte, offset int, v uint64) int {
-	data[offset] = uint8(v)
-	data[offset+1] = uint8(v >> 8)
-	data[offset+2] = uint8(v >> 16)
-	data[offset+3] = uint8(v >> 24)
-	data[offset+4] = uint8(v >> 32)
-	data[offset+5] = uint8(v >> 40)
-	data[offset+6] = uint8(v >> 48)
-	data[offset+7] = uint8(v >> 56)
-	return offset + 8
-}
-func encodeFixed32Test(data []byte, offset int, v uint32) int {
-	data[offset] = uint8(v)
-	data[offset+1] = uint8(v >> 8)
-	data[offset+2] = uint8(v >> 16)
-	data[offset+3] = uint8(v >> 24)
-	return offset + 4
-}
 func encodeVarintTest(data []byte, offset int, v uint64) int {
 	for v >= 1<<7 {
 		data[offset] = uint8(v&0x7f | 0x80)
@@ -689,9 +643,6 @@ func sovTest(x uint64) (n int) {
 	}
 	return n
 }
-func sozTest(x uint64) (n int) {
-	return sovTest(uint64((x << 1) ^ uint64((int64(x) >> 63))))
-}
 func (this *ResultStatus) String() string {
 	if this == nil {
 		return "nil"
@@ -742,14 +693,6 @@ func (this *PubKeyEd25519) String() string {
 	}, "")
 	return s
 }
-func valueToStringTest(v interface{}) string {
-	rv := reflect.ValueOf(v)
-	if rv.IsNil() {
-		return "nil"
-	}
-	pv := reflect.Indirect(rv).Interface()
-	return fmt.Sprintf("*%v", pv)
-}
 func (m *ResultStatus) Unmarshal(data []byte) error {
 	var hasFields [1]uint64
 	l := len(data)
diff --git a/blockchain/pool.go b/blockchain/pool.go
index 47e59711e..1c5a78565 100644
--- a/blockchain/pool.go
+++ b/blockchain/pool.go
@@ -232,7 +232,7 @@ func (pool *BlockPool) AddBlock(peerID string, block *types.Block, blockSize int
 	}
 }
 
-// MaxPeerHeight returns the heighest height reported by a peer
+// MaxPeerHeight returns the highest height reported by a peer.
 func (pool *BlockPool) MaxPeerHeight() int {
 	pool.mtx.Lock()
 	defer pool.mtx.Unlock()
@@ -311,7 +311,10 @@ func (pool *BlockPool) makeNextRequester() {
 	pool.requesters[nextHeight] = request
 	pool.numPending++
 
-	request.Start()
+	_, err := request.Start()
+	if err != nil {
+		request.Logger.Error("Error starting request", "err", err)
+	}
 }
 
 func (pool *BlockPool) sendRequest(height int, peerID string) {
diff --git a/blockchain/pool_test.go b/blockchain/pool_test.go
index a1fce2da8..5c4c8aa3b 100644
--- a/blockchain/pool_test.go
+++ b/blockchain/pool_test.go
@@ -36,7 +36,12 @@ func TestBasic(t *testing.T) {
 	requestsCh := make(chan BlockRequest, 100)
 	pool := NewBlockPool(start, requestsCh, timeoutsCh)
 	pool.SetLogger(log.TestingLogger())
-	pool.Start()
+
+	_, err := pool.Start()
+	if err != nil {
+		t.Error(err)
+	}
+
 	defer pool.Stop()
 
 	// Introduce each peer.
@@ -88,7 +93,10 @@ func TestTimeout(t *testing.T) {
 	requestsCh := make(chan BlockRequest, 100)
 	pool := NewBlockPool(start, requestsCh, timeoutsCh)
 	pool.SetLogger(log.TestingLogger())
-	pool.Start()
+	_, err := pool.Start()
+	if err != nil {
+		t.Error(err)
+	}
 	defer pool.Stop()
 
 	for _, peer := range peers {
diff --git a/blockchain/reactor.go b/blockchain/reactor.go
index 64e5e9377..4d20e777e 100644
--- a/blockchain/reactor.go
+++ b/blockchain/reactor.go
@@ -88,7 +88,9 @@ func (bcR *BlockchainReactor) SetLogger(l log.Logger) {
 
 // OnStart implements cmn.Service.
 func (bcR *BlockchainReactor) OnStart() error {
-	bcR.BaseReactor.OnStart()
+	if err := bcR.BaseReactor.OnStart(); err != nil {
+		return err
+	}
 	if bcR.fastSync {
 		_, err := bcR.pool.Start()
 		if err != nil {
@@ -108,7 +110,7 @@ func (bcR *BlockchainReactor) OnStop() {
 // GetChannels implements Reactor
 func (bcR *BlockchainReactor) GetChannels() []*p2p.ChannelDescriptor {
 	return []*p2p.ChannelDescriptor{
-		&p2p.ChannelDescriptor{
+		{
 			ID:                BlockchainChannel,
 			Priority:          10,
 			SendQueueCapacity: 1000,
@@ -226,7 +228,7 @@ FOR_LOOP:
 			}
 		case <-statusUpdateTicker.C:
 			// ask for status updates
-			go bcR.BroadcastStatusRequest()
+			go bcR.BroadcastStatusRequest() // nolint: errcheck
 		case <-switchToConsensusTicker.C:
 			height, numPending, lenRequesters := bcR.pool.GetStatus()
 			outbound, inbound, _ := bcR.Switch.NumPeers()
diff --git a/blockchain/store.go b/blockchain/store.go
index 5bf854775..bcd10856f 100644
--- a/blockchain/store.go
+++ b/blockchain/store.go
@@ -7,9 +7,9 @@ import (
 	"io"
 	"sync"
 
-	wire "github.com/tendermint/go-wire"
+	"github.com/tendermint/go-wire"
 	"github.com/tendermint/tendermint/types"
-	. "github.com/tendermint/tmlibs/common"
+	cmn "github.com/tendermint/tmlibs/common"
 	dbm "github.com/tendermint/tmlibs/db"
 )
 
@@ -67,7 +67,7 @@ func (bs *BlockStore) LoadBlock(height int) *types.Block {
 	}
 	blockMeta := wire.ReadBinary(&types.BlockMeta{}, r, 0, &n, &err).(*types.BlockMeta)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading block meta: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading block meta: %v", err))
 	}
 	bytez := []byte{}
 	for i := 0; i < blockMeta.BlockID.PartsHeader.Total; i++ {
@@ -76,7 +76,7 @@ func (bs *BlockStore) LoadBlock(height int) *types.Block {
 	}
 	block := wire.ReadBinary(&types.Block{}, bytes.NewReader(bytez), 0, &n, &err).(*types.Block)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading block: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading block: %v", err))
 	}
 	return block
 }
@@ -90,7 +90,7 @@ func (bs *BlockStore) LoadBlockPart(height int, index int) *types.Part {
 	}
 	part := wire.ReadBinary(&types.Part{}, r, 0, &n, &err).(*types.Part)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading block part: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading block part: %v", err))
 	}
 	return part
 }
@@ -104,7 +104,7 @@ func (bs *BlockStore) LoadBlockMeta(height int) *types.BlockMeta {
 	}
 	blockMeta := wire.ReadBinary(&types.BlockMeta{}, r, 0, &n, &err).(*types.BlockMeta)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading block meta: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading block meta: %v", err))
 	}
 	return blockMeta
 }
@@ -120,7 +120,7 @@ func (bs *BlockStore) LoadBlockCommit(height int) *types.Commit {
 	}
 	commit := wire.ReadBinary(&types.Commit{}, r, 0, &n, &err).(*types.Commit)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading commit: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading commit: %v", err))
 	}
 	return commit
 }
@@ -135,7 +135,7 @@ func (bs *BlockStore) LoadSeenCommit(height int) *types.Commit {
 	}
 	commit := wire.ReadBinary(&types.Commit{}, r, 0, &n, &err).(*types.Commit)
 	if err != nil {
-		PanicCrisis(Fmt("Error reading commit: %v", err))
+		cmn.PanicCrisis(cmn.Fmt("Error reading commit: %v", err))
 	}
 	return commit
 }
@@ -148,10 +148,10 @@ func (bs *BlockStore) LoadSeenCommit(height int) *types.Commit {
 func (bs *BlockStore) SaveBlock(block *types.Block, blockParts *types.PartSet, seenCommit *types.Commit) {
 	height := block.Height
 	if height != bs.Height()+1 {
-		PanicSanity(Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.Height()+1, height))
+		cmn.PanicSanity(cmn.Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.Height()+1, height))
 	}
 	if !blockParts.IsComplete() {
-		PanicSanity(Fmt("BlockStore can only save complete block part sets"))
+		cmn.PanicSanity(cmn.Fmt("BlockStore can only save complete block part sets"))
 	}
 
 	// Save block meta
@@ -187,7 +187,7 @@ func (bs *BlockStore) SaveBlock(block *types.Block, blockParts *types.PartSet, s
 
 func (bs *BlockStore) saveBlockPart(height int, index int, part *types.Part) {
 	if height != bs.Height()+1 {
-		PanicSanity(Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.Height()+1, height))
+		cmn.PanicSanity(cmn.Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.Height()+1, height))
 	}
 	partBytes := wire.BinaryBytes(part)
 	bs.db.Set(calcBlockPartKey(height, index), partBytes)
@@ -222,7 +222,7 @@ type BlockStoreStateJSON struct {
 func (bsj BlockStoreStateJSON) Save(db dbm.DB) {
 	bytes, err := json.Marshal(bsj)
 	if err != nil {
-		PanicSanity(Fmt("Could not marshal state bytes: %v", err))
+		cmn.PanicSanity(cmn.Fmt("Could not marshal state bytes: %v", err))
 	}
 	db.SetSync(blockStoreKey, bytes)
 }
@@ -237,7 +237,7 @@ func LoadBlockStoreStateJSON(db dbm.DB) BlockStoreStateJSON {
 	bsj := BlockStoreStateJSON{}
 	err := json.Unmarshal(bytes, &bsj)
 	if err != nil {
-		PanicCrisis(Fmt("Could not unmarshal bytes: %X", bytes))
+		cmn.PanicCrisis(cmn.Fmt("Could not unmarshal bytes: %X", bytes))
 	}
 	return bsj
 }
diff --git a/cmd/tendermint/commands/gen_validator.go b/cmd/tendermint/commands/gen_validator.go
index 984176d2a..59fe30128 100644
--- a/cmd/tendermint/commands/gen_validator.go
+++ b/cmd/tendermint/commands/gen_validator.go
@@ -19,7 +19,10 @@ var GenValidatorCmd = &cobra.Command{
 
 func genValidator(cmd *cobra.Command, args []string) {
 	privValidator := types.GenPrivValidatorFS("")
-	privValidatorJSONBytes, _ := json.MarshalIndent(privValidator, "", "\t")
+	privValidatorJSONBytes, err := json.MarshalIndent(privValidator, "", "\t")
+	if err != nil {
+		panic(err)
+	}
 	fmt.Printf(`%v
 `, string(privValidatorJSONBytes))
 }
diff --git a/cmd/tendermint/commands/init.go b/cmd/tendermint/commands/init.go
index cbafac3ef..e8f22eb1c 100644
--- a/cmd/tendermint/commands/init.go
+++ b/cmd/tendermint/commands/init.go
@@ -28,12 +28,14 @@ func initFiles(cmd *cobra.Command, args []string) {
 			genDoc := types.GenesisDoc{
 				ChainID: cmn.Fmt("test-chain-%v", cmn.RandStr(6)),
 			}
-			genDoc.Validators = []types.GenesisValidator{types.GenesisValidator{
+			genDoc.Validators = []types.GenesisValidator{{
 				PubKey: privValidator.GetPubKey(),
 				Power:  10,
 			}}
 
-			genDoc.SaveAs(genFile)
+			if err := genDoc.SaveAs(genFile); err != nil {
+				panic(err)
+			}
 		}
 
 		logger.Info("Initialized tendermint", "genesis", config.GenesisFile(), "priv_validator", config.PrivValidatorFile())
diff --git a/cmd/tendermint/commands/reset_priv_validator.go b/cmd/tendermint/commands/reset_priv_validator.go
index b9c08715f..513365237 100644
--- a/cmd/tendermint/commands/reset_priv_validator.go
+++ b/cmd/tendermint/commands/reset_priv_validator.go
@@ -25,10 +25,13 @@ var ResetPrivValidatorCmd = &cobra.Command{
 }
 
 // ResetAll removes the privValidator files.
-// Exported so other CLI tools can use  it
+// Exported so other CLI tools can use it.
 func ResetAll(dbDir, privValFile string, logger log.Logger) {
 	resetPrivValidatorFS(privValFile, logger)
-	os.RemoveAll(dbDir)
+	if err := os.RemoveAll(dbDir); err != nil {
+		logger.Error("Error removing directory", "err", err)
+		return
+	}
 	logger.Info("Removed all data", "dir", dbDir)
 }
 
diff --git a/cmd/tendermint/commands/root_test.go b/cmd/tendermint/commands/root_test.go
index 7c3bf801b..b4e30d980 100644
--- a/cmd/tendermint/commands/root_test.go
+++ b/cmd/tendermint/commands/root_test.go
@@ -26,8 +26,12 @@ const (
 // modify in the test cases.
 // NOTE: it unsets all TM* env variables.
 func isolate(cmds ...*cobra.Command) cli.Executable {
-	os.Unsetenv("TMHOME")
-	os.Unsetenv("TM_HOME")
+	if err := os.Unsetenv("TMHOME"); err != nil {
+		panic(err)
+	}
+	if err := os.Unsetenv("TM_HOME"); err != nil {
+		panic(err)
+	}
 
 	viper.Reset()
 	config = cfg.DefaultConfig()
diff --git a/cmd/tendermint/commands/testnet.go b/cmd/tendermint/commands/testnet.go
index ac6f337a9..2c859df2b 100644
--- a/cmd/tendermint/commands/testnet.go
+++ b/cmd/tendermint/commands/testnet.go
@@ -63,7 +63,9 @@ func testnetFiles(cmd *cobra.Command, args []string) {
 	// Write genesis file.
 	for i := 0; i < nValidators; i++ {
 		mach := cmn.Fmt("mach%d", i)
-		genDoc.SaveAs(path.Join(dataDir, mach, "genesis.json"))
+		if err := genDoc.SaveAs(path.Join(dataDir, mach, "genesis.json")); err != nil {
+			panic(err)
+		}
 	}
 
 	fmt.Println(cmn.Fmt("Successfully initialized %v node directories", nValidators))
diff --git a/cmd/tendermint/main.go b/cmd/tendermint/main.go
index 86ca1531d..a46f227c5 100644
--- a/cmd/tendermint/main.go
+++ b/cmd/tendermint/main.go
@@ -37,5 +37,7 @@ func main() {
 	rootCmd.AddCommand(cmd.NewRunNodeCmd(nodeFunc))
 
 	cmd := cli.PrepareBaseCmd(rootCmd, "TM", os.ExpandEnv("$HOME/.tendermint"))
-	cmd.Execute()
+	if err := cmd.Execute(); err != nil {
+		panic(err)
+	}
 }
diff --git a/config/toml.go b/config/toml.go
index 5dcbe5332..ec70ab75d 100644
--- a/config/toml.go
+++ b/config/toml.go
@@ -12,8 +12,12 @@ import (
 /****** these are for production settings ***********/
 
 func EnsureRoot(rootDir string) {
-	cmn.EnsureDir(rootDir, 0700)
-	cmn.EnsureDir(rootDir+"/data", 0700)
+	if err := cmn.EnsureDir(rootDir, 0700); err != nil {
+		cmn.PanicSanity(err.Error())
+	}
+	if err := cmn.EnsureDir(rootDir+"/data", 0700); err != nil {
+		cmn.PanicSanity(err.Error())
+	}
 
 	configFilePath := path.Join(rootDir, "config.toml")
 
@@ -53,21 +57,23 @@ func ResetTestRoot(testName string) *Config {
 	rootDir = filepath.Join(rootDir, testName)
 	// Remove ~/.tendermint_test_bak
 	if cmn.FileExists(rootDir + "_bak") {
-		err := os.RemoveAll(rootDir + "_bak")
-		if err != nil {
+		if err := os.RemoveAll(rootDir + "_bak"); err != nil {
 			cmn.PanicSanity(err.Error())
 		}
 	}
 	// Move ~/.tendermint_test to ~/.tendermint_test_bak
 	if cmn.FileExists(rootDir) {
-		err := os.Rename(rootDir, rootDir+"_bak")
-		if err != nil {
+		if err := os.Rename(rootDir, rootDir+"_bak"); err != nil {
 			cmn.PanicSanity(err.Error())
 		}
 	}
 	// Create new dir
-	cmn.EnsureDir(rootDir, 0700)
-	cmn.EnsureDir(rootDir+"/data", 0700)
+	if err := cmn.EnsureDir(rootDir, 0700); err != nil {
+		cmn.PanicSanity(err.Error())
+	}
+	if err := cmn.EnsureDir(rootDir+"/data", 0700); err != nil {
+		cmn.PanicSanity(err.Error())
+	}
 
 	configFilePath := path.Join(rootDir, "config.toml")
 	genesisFilePath := path.Join(rootDir, "genesis.json")
diff --git a/config/toml_test.go b/config/toml_test.go
index d8f372aee..bf3bf58f7 100644
--- a/config/toml_test.go
+++ b/config/toml_test.go
@@ -24,7 +24,7 @@ func TestEnsureRoot(t *testing.T) {
 	// setup temp dir for test
 	tmpDir, err := ioutil.TempDir("", "config-test")
 	require.Nil(err)
-	defer os.RemoveAll(tmpDir)
+	defer os.RemoveAll(tmpDir) // nolint: errcheck
 
 	// create root dir
 	EnsureRoot(tmpDir)
diff --git a/consensus/byzantine_test.go b/consensus/byzantine_test.go
index 6bd7bdd4a..9ac163eb9 100644
--- a/consensus/byzantine_test.go
+++ b/consensus/byzantine_test.go
@@ -70,7 +70,7 @@ func TestByzantine(t *testing.T) {
 		conR.SetLogger(logger.With("validator", i))
 		conR.SetEventBus(eventBus)
 
-		var conRI p2p.Reactor
+		var conRI p2p.Reactor // nolint: gotype, gosimple
 		conRI = conR
 
 		if i == 0 {
@@ -170,13 +170,17 @@ func byzantineDecideProposalFunc(t *testing.T, height, round int, cs *ConsensusS
 	block1, blockParts1 := cs.createProposalBlock()
 	polRound, polBlockID := cs.Votes.POLInfo()
 	proposal1 := types.NewProposal(height, round, blockParts1.Header(), polRound, polBlockID)
-	cs.privValidator.SignProposal(cs.state.ChainID, proposal1) // byzantine doesnt err
+	if err := cs.privValidator.SignProposal(cs.state.ChainID, proposal1); err != nil {
+		t.Error(err)
+	}
 
 	// Create a new proposal block from state/txs from the mempool.
 	block2, blockParts2 := cs.createProposalBlock()
 	polRound, polBlockID = cs.Votes.POLInfo()
 	proposal2 := types.NewProposal(height, round, blockParts2.Header(), polRound, polBlockID)
-	cs.privValidator.SignProposal(cs.state.ChainID, proposal2) // byzantine doesnt err
+	if err := cs.privValidator.SignProposal(cs.state.ChainID, proposal2); err != nil {
+		t.Error(err)
+	}
 
 	block1Hash := block1.Hash()
 	block2Hash := block2.Hash()
@@ -289,12 +293,12 @@ func (privVal *ByzantinePrivValidator) SignVote(chainID string, vote *types.Vote
 }
 
 func (privVal *ByzantinePrivValidator) SignProposal(chainID string, proposal *types.Proposal) (err error) {
-	proposal.Signature, err = privVal.Sign(types.SignBytes(chainID, proposal))
+	proposal.Signature, _ = privVal.Sign(types.SignBytes(chainID, proposal))
 	return nil
 }
 
 func (privVal *ByzantinePrivValidator) SignHeartbeat(chainID string, heartbeat *types.Heartbeat) (err error) {
-	heartbeat.Signature, err = privVal.Sign(types.SignBytes(chainID, heartbeat))
+	heartbeat.Signature, _ = privVal.Sign(types.SignBytes(chainID, heartbeat))
 	return nil
 }
 
diff --git a/consensus/common_test.go b/consensus/common_test.go
index 50793e651..8528b0a95 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -268,7 +268,6 @@ func newConsensusStateWithConfigAndBlockStore(thisConfig *cfg.Config, state *sm.
 	eventBus.SetLogger(log.TestingLogger().With("module", "events"))
 	eventBus.Start()
 	cs.SetEventBus(eventBus)
-
 	return cs
 }
 
diff --git a/consensus/mempool_test.go b/consensus/mempool_test.go
index 3314caad1..73f676342 100644
--- a/consensus/mempool_test.go
+++ b/consensus/mempool_test.go
@@ -5,6 +5,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+
 	abci "github.com/tendermint/abci/types"
 	"github.com/tendermint/tendermint/types"
 	cmn "github.com/tendermint/tmlibs/common"
@@ -118,8 +120,12 @@ func TestRmBadTx(t *testing.T) {
 	// increment the counter by 1
 	txBytes := make([]byte, 8)
 	binary.BigEndian.PutUint64(txBytes, uint64(0))
-	app.DeliverTx(txBytes)
-	app.Commit()
+
+	resDeliver := app.DeliverTx(txBytes)
+	assert.False(t, resDeliver.IsErr(), cmn.Fmt("expected no error. got %v", resDeliver))
+
+	resCommit := app.Commit()
+	assert.False(t, resCommit.IsErr(), cmn.Fmt("expected no error. got %v", resCommit))
 
 	emptyMempoolCh := make(chan struct{})
 	checkTxRespCh := make(chan struct{})
diff --git a/consensus/reactor.go b/consensus/reactor.go
index 11cd07501..e873ddde9 100644
--- a/consensus/reactor.go
+++ b/consensus/reactor.go
@@ -55,7 +55,9 @@ func NewConsensusReactor(consensusState *ConsensusState, fastSync bool) *Consens
 // OnStart implements BaseService.
 func (conR *ConsensusReactor) OnStart() error {
 	conR.Logger.Info("ConsensusReactor ", "fastSync", conR.FastSync())
-	conR.BaseReactor.OnStart()
+	if err := conR.BaseReactor.OnStart(); err != nil {
+		return err
+	}
 
 	err := conR.startBroadcastRoutine()
 	if err != nil {
@@ -95,31 +97,34 @@ func (conR *ConsensusReactor) SwitchToConsensus(state *sm.State, blocksSynced in
 		// dont bother with the WAL if we fast synced
 		conR.conS.doWALCatchup = false
 	}
-	conR.conS.Start()
+	_, err := conR.conS.Start()
+	if err != nil {
+		conR.Logger.Error("Error starting conS", "err", err)
+	}
 }
 
 // GetChannels implements Reactor
 func (conR *ConsensusReactor) GetChannels() []*p2p.ChannelDescriptor {
 	// TODO optimize
 	return []*p2p.ChannelDescriptor{
-		&p2p.ChannelDescriptor{
+		{
 			ID:                StateChannel,
 			Priority:          5,
 			SendQueueCapacity: 100,
 		},
-		&p2p.ChannelDescriptor{
+		{
 			ID:                 DataChannel, // maybe split between gossiping current block and catchup stuff
 			Priority:           10,          // once we gossip the whole block there's nothing left to send until next height or round
 			SendQueueCapacity:  100,
 			RecvBufferCapacity: 50 * 4096,
 		},
-		&p2p.ChannelDescriptor{
+		{
 			ID:                 VoteChannel,
 			Priority:           5,
 			SendQueueCapacity:  100,
 			RecvBufferCapacity: 100 * 100,
 		},
-		&p2p.ChannelDescriptor{
+		{
 			ID:                 VoteSetBitsChannel,
 			Priority:           1,
 			SendQueueCapacity:  2,
diff --git a/consensus/reactor_test.go b/consensus/reactor_test.go
index 45e94a121..458ff2c44 100644
--- a/consensus/reactor_test.go
+++ b/consensus/reactor_test.go
@@ -112,7 +112,9 @@ func TestReactorProposalHeartbeats(t *testing.T) {
 	}, css)
 
 	// send a tx
-	css[3].mempool.CheckTx([]byte{1, 2, 3}, nil)
+	if err := css[3].mempool.CheckTx([]byte{1, 2, 3}, nil); err != nil {
+		//t.Fatal(err)
+	}
 
 	// wait till everyone makes the first new block
 	timeoutWaitGroup(t, N, func(wg *sync.WaitGroup, j int) {
diff --git a/consensus/replay.go b/consensus/replay.go
index 49aa5e7fe..349eade04 100644
--- a/consensus/replay.go
+++ b/consensus/replay.go
@@ -7,12 +7,12 @@ import (
 	"hash/crc32"
 	"io"
 	"reflect"
-	"strconv"
-	"strings"
+	//"strconv"
+	//"strings"
 	"time"
 
 	abci "github.com/tendermint/abci/types"
-	auto "github.com/tendermint/tmlibs/autofile"
+	//auto "github.com/tendermint/tmlibs/autofile"
 	cmn "github.com/tendermint/tmlibs/common"
 	"github.com/tendermint/tmlibs/log"
 
@@ -99,8 +99,13 @@ func (cs *ConsensusState) catchupReplay(csHeight int) error {
 	// NOTE: This is just a sanity check. As far as we know things work fine without it,
 	// and Handshake could reuse ConsensusState if it weren't for this check (since we can crash after writing ENDHEIGHT).
 	gr, found, err := cs.wal.SearchForEndHeight(uint64(csHeight))
+	if err != nil {
+		return err
+	}
 	if gr != nil {
-		gr.Close()
+		if err := gr.Close(); err != nil {
+			return err
+		}
 	}
 	if found {
 		return fmt.Errorf("WAL should not contain #ENDHEIGHT %d.", csHeight)
@@ -116,7 +121,7 @@ func (cs *ConsensusState) catchupReplay(csHeight int) error {
 	if !found {
 		return errors.New(cmn.Fmt("Cannot replay height %d. WAL does not contain #ENDHEIGHT for %d.", csHeight, csHeight-1))
 	}
-	defer gr.Close()
+	defer gr.Close() // nolint: errcheck
 
 	cs.Logger.Info("Catchup by replaying consensus messages", "height", csHeight)
 
@@ -145,6 +150,7 @@ func (cs *ConsensusState) catchupReplay(csHeight int) error {
 
 // Parses marker lines of the form:
 // #ENDHEIGHT: 12345
+/*
 func makeHeightSearchFunc(height int) auto.SearchFunc {
 	return func(line string) (int, error) {
 		line = strings.TrimRight(line, "\n")
@@ -164,7 +170,7 @@ func makeHeightSearchFunc(height int) auto.SearchFunc {
 			return -1, nil
 		}
 	}
-}
+}*/
 
 //----------------------------------------------
 // Recover from failure during block processing
@@ -230,7 +236,9 @@ func (h *Handshaker) ReplayBlocks(appHash []byte, appBlockHeight int, proxyApp p
 	// If appBlockHeight == 0 it means that we are at genesis and hence should send InitChain
 	if appBlockHeight == 0 {
 		validators := types.TM2PB.Validators(h.state.Validators)
-		proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators})
+		if err := proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators}); err != nil {
+			return nil, err
+		}
 	}
 
 	// First handle edge cases and constraints on the storeBlockHeight
@@ -363,7 +371,10 @@ func newMockProxyApp(appHash []byte, abciResponses *sm.ABCIResponses) proxy.AppC
 		abciResponses: abciResponses,
 	})
 	cli, _ := clientCreator.NewABCIClient()
-	cli.Start()
+	_, err := cli.Start()
+	if err != nil {
+		panic(err)
+	}
 	return proxy.NewAppConnConsensus(cli)
 }
 
diff --git a/consensus/replay_file.go b/consensus/replay_file.go
index 6b52b5b09..ba7b12654 100644
--- a/consensus/replay_file.go
+++ b/consensus/replay_file.go
@@ -59,13 +59,13 @@ func (cs *ConsensusState) ReplayFile(file string, console bool) error {
 	defer cs.eventBus.Unsubscribe(ctx, subscriber, types.EventQueryNewRoundStep)
 
 	// just open the file for reading, no need to use wal
-	fp, err := os.OpenFile(file, os.O_RDONLY, 0666)
+	fp, err := os.OpenFile(file, os.O_RDONLY, 0600)
 	if err != nil {
 		return err
 	}
 
 	pb := newPlayback(file, fp, cs, cs.state.Copy())
-	defer pb.fp.Close()
+	defer pb.fp.Close() // nolint: errcheck
 
 	var nextN int // apply N msgs in a row
 	var msg *TimedWALMessage
@@ -127,8 +127,10 @@ func (pb *playback) replayReset(count int, newStepCh chan interface{}) error {
 	newCS.SetEventBus(pb.cs.eventBus)
 	newCS.startForReplay()
 
-	pb.fp.Close()
-	fp, err := os.OpenFile(pb.fileName, os.O_RDONLY, 0666)
+	if err := pb.fp.Close(); err != nil {
+		return err
+	}
+	fp, err := os.OpenFile(pb.fileName, os.O_RDONLY, 0600)
 	if err != nil {
 		return err
 	}
@@ -220,7 +222,9 @@ func (pb *playback) replayConsoleLoop() int {
 			defer pb.cs.eventBus.Unsubscribe(ctx, subscriber, types.EventQueryNewRoundStep)
 
 			if len(tokens) == 1 {
-				pb.replayReset(1, newStepCh)
+				if err := pb.replayReset(1, newStepCh); err != nil {
+					pb.cs.Logger.Error("Replay reset error", "err", err)
+				}
 			} else {
 				i, err := strconv.Atoi(tokens[1])
 				if err != nil {
@@ -228,7 +232,9 @@ func (pb *playback) replayConsoleLoop() int {
 				} else if i > pb.count {
 					fmt.Printf("argument to back must not be larger than the current count (%d)\n", pb.count)
 				} else {
-					pb.replayReset(i, newStepCh)
+					if err := pb.replayReset(i, newStepCh); err != nil {
+						pb.cs.Logger.Error("Replay reset error", "err", err)
+					}
 				}
 			}
 
diff --git a/consensus/replay_test.go b/consensus/replay_test.go
index a5d3f0883..0403b8a48 100644
--- a/consensus/replay_test.go
+++ b/consensus/replay_test.go
@@ -411,7 +411,9 @@ func buildAppStateFromChain(proxyApp proxy.AppConns,
 	}
 
 	validators := types.TM2PB.Validators(state.Validators)
-	proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators})
+	if err := proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators}); err != nil {
+		panic(err)
+	}
 
 	defer proxyApp.Stop()
 	switch mode {
@@ -445,7 +447,9 @@ func buildTMStateFromChain(config *cfg.Config, state *sm.State, chain []*types.B
 	defer proxyApp.Stop()
 
 	validators := types.TM2PB.Validators(state.Validators)
-	proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators})
+	if err := proxyApp.Consensus().InitChainSync(abci.RequestInitChain{validators}); err != nil {
+		panic(err)
+	}
 
 	var latestAppHash []byte
 
@@ -486,7 +490,7 @@ func makeBlockchainFromWAL(wal WAL) ([]*types.Block, []*types.Commit, error) {
 	if !found {
 		return nil, nil, errors.New(cmn.Fmt("WAL does not contain height %d.", 1))
 	}
-	defer gr.Close()
+	defer gr.Close() // nolint: errcheck
 
 	// log.Notice("Build a blockchain by reading from the WAL")
 
diff --git a/consensus/state.go b/consensus/state.go
index c65976d79..a535a1017 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -225,11 +225,14 @@ func (cs *ConsensusState) OnStart() error {
 	}
 
 	// we need the timeoutRoutine for replay so
-	//  we don't block on the tick chan.
+	// we don't block on the tick chan.
 	// NOTE: we will get a build up of garbage go routines
-	//  firing on the tockChan until the receiveRoutine is started
-	//  to deal with them (by that point, at most one will be valid)
-	cs.timeoutTicker.Start()
+	// firing on the tockChan until the receiveRoutine is started
+	// to deal with them (by that point, at most one will be valid)
+	_, err := cs.timeoutTicker.Start()
+	if err != nil {
+		return err
+	}
 
 	// we may have lost some votes if the process crashed
 	// reload from consensus log to catchup
@@ -254,7 +257,11 @@ func (cs *ConsensusState) OnStart() error {
 // timeoutRoutine: receive requests for timeouts on tickChan and fire timeouts on tockChan
 // receiveRoutine: serializes processing of proposoals, block parts, votes; coordinates state transitions
 func (cs *ConsensusState) startRoutines(maxSteps int) {
-	cs.timeoutTicker.Start()
+	_, err := cs.timeoutTicker.Start()
+	if err != nil {
+		cs.Logger.Error("Error starting timeout ticker", "err", err)
+		return
+	}
 	go cs.receiveRoutine(maxSteps)
 }
 
@@ -338,12 +345,16 @@ func (cs *ConsensusState) AddProposalBlockPart(height, round int, part *types.Pa
 
 // SetProposalAndBlock inputs the proposal and all block parts.
 func (cs *ConsensusState) SetProposalAndBlock(proposal *types.Proposal, block *types.Block, parts *types.PartSet, peerKey string) error {
-	cs.SetProposal(proposal, peerKey)
+	if err := cs.SetProposal(proposal, peerKey); err != nil {
+		return err
+	}
 	for i := 0; i < parts.Total(); i++ {
 		part := parts.GetPart(i)
-		cs.AddProposalBlockPart(proposal.Height, proposal.Round, part, peerKey)
+		if err := cs.AddProposalBlockPart(proposal.Height, proposal.Round, part, peerKey); err != nil {
+			return err
+		}
 	}
-	return nil // TODO errors
+	return nil
 }
 
 //------------------------------------------------------------
@@ -361,7 +372,7 @@ func (cs *ConsensusState) updateRoundStep(round int, step cstypes.RoundStepType)
 // enterNewRound(height, 0) at cs.StartTime.
 func (cs *ConsensusState) scheduleRound0(rs *cstypes.RoundState) {
 	//cs.Logger.Info("scheduleRound0", "now", time.Now(), "startTime", cs.StartTime)
-	sleepDuration := rs.StartTime.Sub(time.Now())
+	sleepDuration := rs.StartTime.Sub(time.Now()) // nolint: gotype, gosimple
 	cs.scheduleTimeout(sleepDuration, rs.Height, 0, cstypes.RoundStepNewHeight)
 }
 
@@ -692,10 +703,7 @@ func (cs *ConsensusState) needProofBlock(height int) bool {
 	}
 
 	lastBlockMeta := cs.blockStore.LoadBlockMeta(height - 1)
-	if !bytes.Equal(cs.state.AppHash, lastBlockMeta.Header.AppHash) {
-		return true
-	}
-	return false
+	return !bytes.Equal(cs.state.AppHash, lastBlockMeta.Header.AppHash)
 }
 
 func (cs *ConsensusState) proposalHeartbeat(height, round int) {
diff --git a/consensus/state_test.go b/consensus/state_test.go
index 49ec1185c..ecccafed4 100644
--- a/consensus/state_test.go
+++ b/consensus/state_test.go
@@ -209,7 +209,9 @@ func TestBadProposal(t *testing.T) {
 	}
 
 	// set the proposal block
-	cs1.SetProposalAndBlock(proposal, propBlock, propBlockParts, "some peer")
+	if err := cs1.SetProposalAndBlock(proposal, propBlock, propBlockParts, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 
 	// start the machine
 	startTestRound(cs1, height, round)
@@ -478,7 +480,9 @@ func TestLockNoPOL(t *testing.T) {
 
 	// now we're on a new round and not the proposer
 	// so set the proposal block
-	cs1.SetProposalAndBlock(prop, propBlock, propBlock.MakePartSet(partSize), "")
+	if err := cs1.SetProposalAndBlock(prop, propBlock, propBlock.MakePartSet(partSize), ""); err != nil {
+		t.Fatal(err)
+	}
 
 	<-proposalCh
 	<-voteCh // prevote
@@ -555,7 +559,9 @@ func TestLockPOLRelock(t *testing.T) {
 	<-timeoutWaitCh
 
 	//XXX: this isnt guaranteed to get there before the timeoutPropose ...
-	cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer")
+	if err := cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 
 	<-newRoundCh
 	t.Log("### ONTO ROUND 1")
@@ -667,7 +673,9 @@ func TestLockPOLUnlock(t *testing.T) {
 	lockedBlockHash := rs.LockedBlock.Hash()
 
 	//XXX: this isnt guaranteed to get there before the timeoutPropose ...
-	cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer")
+	if err := cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 
 	<-newRoundCh
 	t.Log("#### ONTO ROUND 1")
@@ -754,7 +762,9 @@ func TestLockPOLSafety1(t *testing.T) {
 	incrementRound(vs2, vs3, vs4)
 
 	//XXX: this isnt guaranteed to get there before the timeoutPropose ...
-	cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer")
+	if err := cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 
 	<-newRoundCh
 	t.Log("### ONTO ROUND 1")
@@ -866,7 +876,9 @@ func TestLockPOLSafety2(t *testing.T) {
 	startTestRound(cs1, height, 1)
 	<-newRoundCh
 
-	cs1.SetProposalAndBlock(prop1, propBlock1, propBlockParts1, "some peer")
+	if err := cs1.SetProposalAndBlock(prop1, propBlock1, propBlockParts1, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 	<-proposalCh
 
 	<-voteCh // prevote
@@ -891,7 +903,9 @@ func TestLockPOLSafety2(t *testing.T) {
 	if err := vs3.SignProposal(config.ChainID, newProp); err != nil {
 		t.Fatal(err)
 	}
-	cs1.SetProposalAndBlock(newProp, propBlock0, propBlockParts0, "some peer")
+	if err := cs1.SetProposalAndBlock(newProp, propBlock0, propBlockParts0, "some peer"); err != nil {
+		t.Fatal(err)
+	}
 
 	// Add the pol votes
 	addVotes(cs1, prevotes...)
diff --git a/consensus/wal.go b/consensus/wal.go
index 3f85f7da6..109f5f3f2 100644
--- a/consensus/wal.go
+++ b/consensus/wal.go
@@ -174,7 +174,6 @@ func (wal *baseWAL) SearchForEndHeight(height uint64) (gr *auto.GroupReader, fou
 				}
 			}
 		}
-
 		gr.Close()
 	}
 
@@ -273,7 +272,7 @@ func (dec *WALDecoder) Decode() (*TimedWALMessage, error) {
 	}
 
 	var nn int
-	var res *TimedWALMessage
+	var res *TimedWALMessage // nolint: gosimple
 	res = wire.ReadBinary(&TimedWALMessage{}, bytes.NewBuffer(data), int(length), &nn, &err).(*TimedWALMessage)
 	if err != nil {
 		return nil, fmt.Errorf("failed to decode data: %v", err)
diff --git a/lite/files/provider.go b/lite/files/provider.go
index c2f570a76..faa68dd9b 100644
--- a/lite/files/provider.go
+++ b/lite/files/provider.go
@@ -34,7 +34,7 @@ const (
 	ValDir   = "validators"
 	CheckDir = "checkpoints"
 	dirPerm  = os.FileMode(0755)
-	filePerm = os.FileMode(0644)
+	//filePerm = os.FileMode(0644)
 )
 
 type provider struct {
diff --git a/mempool/mempool.go b/mempool/mempool.go
index caaa034e9..d781500c2 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -189,8 +189,14 @@ func (mem *Mempool) CheckTx(tx types.Tx, cb func(*abci.Response)) (err error) {
 	// WAL
 	if mem.wal != nil {
 		// TODO: Notify administrators when WAL fails
-		mem.wal.Write([]byte(tx))
-		mem.wal.Write([]byte("\n"))
+		_, err := mem.wal.Write([]byte(tx))
+		if err != nil {
+			mem.logger.Error("Error writing to WAL", "err", err)
+		}
+		_, err = mem.wal.Write([]byte("\n"))
+		if err != nil {
+			mem.logger.Error("Error writing to WAL", "err", err)
+		}
 	}
 	// END WAL
 
@@ -331,10 +337,10 @@ func (mem *Mempool) collectTxs(maxTxs int) types.Txs {
 // Update informs the mempool that the given txs were committed and can be discarded.
 // NOTE: this should be called *after* block is committed by consensus.
 // NOTE: unsafe; Lock/Unlock must be managed by caller
-func (mem *Mempool) Update(height int, txs types.Txs) {
-	// TODO: check err ?
-	mem.proxyAppConn.FlushSync() // To flush async resCb calls e.g. from CheckTx
-
+func (mem *Mempool) Update(height int, txs types.Txs) error {
+	if err := mem.proxyAppConn.FlushSync(); err != nil { // To flush async resCb calls e.g. from CheckTx
+		return err
+	}
 	// First, create a lookup map of txns in new txs.
 	txsMap := make(map[string]struct{})
 	for _, tx := range txs {
@@ -357,6 +363,7 @@ func (mem *Mempool) Update(height int, txs types.Txs) {
 		// mem.recheckCursor re-scans mem.txs and possibly removes some txs.
 		// Before mem.Reap(), we should wait for mem.recheckCursor to be nil.
 	}
+	return nil
 }
 
 func (mem *Mempool) filterTxs(blockTxsMap map[string]struct{}) []types.Tx {
diff --git a/mempool/mempool_test.go b/mempool/mempool_test.go
index 46401e88b..7773d9d74 100644
--- a/mempool/mempool_test.go
+++ b/mempool/mempool_test.go
@@ -20,7 +20,10 @@ func newMempoolWithApp(cc proxy.ClientCreator) *Mempool {
 
 	appConnMem, _ := cc.NewABCIClient()
 	appConnMem.SetLogger(log.TestingLogger().With("module", "abci-client", "connection", "mempool"))
-	appConnMem.Start()
+	_, err := appConnMem.Start()
+	if err != nil {
+		panic(err)
+	}
 	mempool := NewMempool(config.Mempool, appConnMem, 0)
 	mempool.SetLogger(log.TestingLogger())
 	return mempool
@@ -49,9 +52,11 @@ func checkTxs(t *testing.T, mempool *Mempool, count int) types.Txs {
 	for i := 0; i < count; i++ {
 		txBytes := make([]byte, 20)
 		txs[i] = txBytes
-		rand.Read(txBytes)
-		err := mempool.CheckTx(txBytes, nil)
+		_, err := rand.Read(txBytes)
 		if err != nil {
+			t.Error(err)
+		}
+		if err := mempool.CheckTx(txBytes, nil); err != nil {
 			t.Fatal("Error after CheckTx: %v", err)
 		}
 	}
@@ -78,7 +83,9 @@ func TestTxsAvailable(t *testing.T) {
 	// it should fire once now for the new height
 	// since there are still txs left
 	committedTxs, txs := txs[:50], txs[50:]
-	mempool.Update(1, committedTxs)
+	if err := mempool.Update(1, committedTxs); err != nil {
+		t.Error(err)
+	}
 	ensureFire(t, mempool.TxsAvailable(), timeoutMS)
 	ensureNoFire(t, mempool.TxsAvailable(), timeoutMS)
 
@@ -88,7 +95,9 @@ func TestTxsAvailable(t *testing.T) {
 
 	// now call update with all the txs. it should not fire as there are no txs left
 	committedTxs = append(txs, moreTxs...)
-	mempool.Update(2, committedTxs)
+	if err := mempool.Update(2, committedTxs); err != nil {
+		t.Error(err)
+	}
 	ensureNoFire(t, mempool.TxsAvailable(), timeoutMS)
 
 	// send a bunch more txs, it should only fire once
@@ -146,7 +155,9 @@ func TestSerialReap(t *testing.T) {
 			binary.BigEndian.PutUint64(txBytes, uint64(i))
 			txs = append(txs, txBytes)
 		}
-		mempool.Update(0, txs)
+		if err := mempool.Update(0, txs); err != nil {
+			t.Error(err)
+		}
 	}
 
 	commitRange := func(start, end int) {
diff --git a/mempool/reactor.go b/mempool/reactor.go
index 6a8765200..9e51d2df5 100644
--- a/mempool/reactor.go
+++ b/mempool/reactor.go
@@ -50,7 +50,7 @@ func (memR *MempoolReactor) SetLogger(l log.Logger) {
 // It returns the list of channels for this reactor.
 func (memR *MempoolReactor) GetChannels() []*p2p.ChannelDescriptor {
 	return []*p2p.ChannelDescriptor{
-		&p2p.ChannelDescriptor{
+		{
 			ID:       MempoolChannel,
 			Priority: 5,
 		},
diff --git a/node/node.go b/node/node.go
index c25c01027..def313943 100644
--- a/node/node.go
+++ b/node/node.go
@@ -384,7 +384,7 @@ func (n *Node) OnStop() {
 	n.eventBus.Stop()
 }
 
-// RunForever waits for an interupt signal and stops the node.
+// RunForever waits for an interrupt signal and stops the node.
 func (n *Node) RunForever() {
 	// Sleep forever and then...
 	cmn.TrapSignal(func() {
@@ -430,7 +430,10 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 		mux := http.NewServeMux()
 		rpcLogger := n.Logger.With("module", "rpc-server")
 		onDisconnect := rpcserver.OnDisconnect(func(remoteAddr string) {
-			n.eventBus.UnsubscribeAll(context.Background(), remoteAddr)
+			err := n.eventBus.UnsubscribeAll(context.Background(), remoteAddr)
+			if err != nil {
+				rpcLogger.Error("Error unsubsribing from all on disconnect", "err", err)
+			}
 		})
 		wm := rpcserver.NewWebsocketManager(rpccore.Routes, onDisconnect)
 		wm.SetLogger(rpcLogger.With("protocol", "websocket"))
diff --git a/node/node_test.go b/node/node_test.go
index 01099459a..645bd2f21 100644
--- a/node/node_test.go
+++ b/node/node_test.go
@@ -19,7 +19,10 @@ func TestNodeStartStop(t *testing.T) {
 	// create & start node
 	n, err := DefaultNewNode(config, log.TestingLogger())
 	assert.NoError(t, err, "expected no err on DefaultNewNode")
-	n.Start()
+	_, err1 := n.Start()
+	if err1 != nil {
+		t.Error(err1)
+	}
 	t.Logf("Started node %v", n.sw.NodeInfo())
 
 	// wait for the node to produce a block
diff --git a/p2p/addrbook.go b/p2p/addrbook.go
index 0b3301060..8f924d129 100644
--- a/p2p/addrbook.go
+++ b/p2p/addrbook.go
@@ -130,7 +130,9 @@ func (a *AddrBook) init() {
 
 // OnStart implements Service.
 func (a *AddrBook) OnStart() error {
-	a.BaseService.OnStart()
+	if err := a.BaseService.OnStart(); err != nil {
+		return err
+	}
 	a.loadFromFile(a.filePath)
 
 	// wg.Add to ensure that any invocation of .Wait()
@@ -369,7 +371,7 @@ func (a *AddrBook) loadFromFile(filePath string) bool {
 	if err != nil {
 		cmn.PanicCrisis(cmn.Fmt("Error opening file %s: %v", filePath, err))
 	}
-	defer r.Close()
+	defer r.Close() // nolint: errcheck
 	aJSON := &addrBookJSON{}
 	dec := json.NewDecoder(r)
 	err = dec.Decode(aJSON)
diff --git a/p2p/connection.go b/p2p/connection.go
index 28b136c77..ad73b68e8 100644
--- a/p2p/connection.go
+++ b/p2p/connection.go
@@ -163,7 +163,9 @@ func NewMConnectionWithConfig(conn net.Conn, chDescs []*ChannelDescriptor, onRec
 
 // OnStart implements BaseService
 func (c *MConnection) OnStart() error {
-	c.BaseService.OnStart()
+	if err := c.BaseService.OnStart(); err != nil {
+		return err
+	}
 	c.quit = make(chan struct{})
 	c.flushTimer = cmn.NewThrottleTimer("flush", c.config.flushThrottle)
 	c.pingTimer = cmn.NewRepeatTimer("ping", pingTimeout)
@@ -182,7 +184,7 @@ func (c *MConnection) OnStop() {
 	if c.quit != nil {
 		close(c.quit)
 	}
-	c.conn.Close()
+	c.conn.Close() // nolint: errcheck
 	// We can't close pong safely here because
 	// recvRoutine may write to it after we've stopped.
 	// Though it doesn't need to get closed at all,
@@ -569,7 +571,7 @@ type Channel struct {
 func newChannel(conn *MConnection, desc ChannelDescriptor) *Channel {
 	desc = desc.FillDefaults()
 	if desc.Priority <= 0 {
-		cmn.PanicSanity("Channel default priority must be a postive integer")
+		cmn.PanicSanity("Channel default priority must be a positive integer")
 	}
 	return &Channel{
 		conn:                    conn,
diff --git a/p2p/connection_test.go b/p2p/connection_test.go
index d74deabfa..11b036dcc 100644
--- a/p2p/connection_test.go
+++ b/p2p/connection_test.go
@@ -32,8 +32,8 @@ func TestMConnectionSend(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	server, client := netPipe()
-	defer server.Close()
-	defer client.Close()
+	defer server.Close() // nolint: errcheck
+	defer client.Close() // nolint: errcheck
 
 	mconn := createTestMConnection(client)
 	_, err := mconn.Start()
@@ -44,12 +44,18 @@ func TestMConnectionSend(t *testing.T) {
 	assert.True(mconn.Send(0x01, msg))
 	// Note: subsequent Send/TrySend calls could pass because we are reading from
 	// the send queue in a separate goroutine.
-	server.Read(make([]byte, len(msg)))
+	_, err = server.Read(make([]byte, len(msg)))
+	if err != nil {
+		t.Error(err)
+	}
 	assert.True(mconn.CanSend(0x01))
 
 	msg = "Spider-Man"
 	assert.True(mconn.TrySend(0x01, msg))
-	server.Read(make([]byte, len(msg)))
+	_, err = server.Read(make([]byte, len(msg)))
+	if err != nil {
+		t.Error(err)
+	}
 
 	assert.False(mconn.CanSend(0x05), "CanSend should return false because channel is unknown")
 	assert.False(mconn.Send(0x05, "Absorbing Man"), "Send should return false because channel is unknown")
@@ -59,8 +65,8 @@ func TestMConnectionReceive(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	server, client := netPipe()
-	defer server.Close()
-	defer client.Close()
+	defer server.Close() // nolint: errcheck
+	defer client.Close() // nolint: errcheck
 
 	receivedCh := make(chan []byte)
 	errorsCh := make(chan interface{})
@@ -97,8 +103,8 @@ func TestMConnectionStatus(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	server, client := netPipe()
-	defer server.Close()
-	defer client.Close()
+	defer server.Close() // nolint: errcheck
+	defer client.Close() // nolint: errcheck
 
 	mconn := createTestMConnection(client)
 	_, err := mconn.Start()
@@ -114,8 +120,8 @@ func TestMConnectionStopsAndReturnsError(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	server, client := netPipe()
-	defer server.Close()
-	defer client.Close()
+	defer server.Close() // nolint: errcheck
+	defer client.Close() // nolint: errcheck
 
 	receivedCh := make(chan []byte)
 	errorsCh := make(chan interface{})
@@ -130,7 +136,9 @@ func TestMConnectionStopsAndReturnsError(t *testing.T) {
 	require.Nil(err)
 	defer mconn.Stop()
 
-	client.Close()
+	if err := client.Close(); err != nil {
+		t.Error(err)
+	}
 
 	select {
 	case receivedBytes := <-receivedCh:
diff --git a/p2p/fuzz.go b/p2p/fuzz.go
index aefac986a..fa16e4a26 100644
--- a/p2p/fuzz.go
+++ b/p2p/fuzz.go
@@ -124,7 +124,7 @@ func (fc *FuzzedConnection) SetWriteDeadline(t time.Time) error {
 
 func (fc *FuzzedConnection) randomDuration() time.Duration {
 	maxDelayMillis := int(fc.config.MaxDelay.Nanoseconds() / 1000)
-	return time.Millisecond * time.Duration(rand.Int()%maxDelayMillis)
+	return time.Millisecond * time.Duration(rand.Int()%maxDelayMillis) // nolint: gas
 }
 
 // implements the fuzz (delay, kill conn)
@@ -143,7 +143,7 @@ func (fc *FuzzedConnection) fuzz() bool {
 		} else if r < fc.config.ProbDropRW+fc.config.ProbDropConn {
 			// XXX: can't this fail because machine precision?
 			// XXX: do we need an error?
-			fc.Close()
+			fc.Close() // nolint: errcheck, gas
 			return true
 		} else if r < fc.config.ProbDropRW+fc.config.ProbDropConn+fc.config.ProbSleep {
 			time.Sleep(fc.randomDuration())
diff --git a/p2p/listener.go b/p2p/listener.go
index 971390974..32a608d6c 100644
--- a/p2p/listener.go
+++ b/p2p/listener.go
@@ -100,19 +100,24 @@ func NewDefaultListener(protocol string, lAddr string, skipUPNP bool, logger log
 		connections: make(chan net.Conn, numBufferedConnections),
 	}
 	dl.BaseService = *cmn.NewBaseService(logger, "DefaultListener", dl)
-	dl.Start() // Started upon construction
+	_, err = dl.Start() // Started upon construction
+	if err != nil {
+		logger.Error("Error starting base service", "err", err)
+	}
 	return dl
 }
 
 func (l *DefaultListener) OnStart() error {
-	l.BaseService.OnStart()
+	if err := l.BaseService.OnStart(); err != nil {
+		return err
+	}
 	go l.listenRoutine()
 	return nil
 }
 
 func (l *DefaultListener) OnStop() {
 	l.BaseService.OnStop()
-	l.listener.Close()
+	l.listener.Close() // nolint: errcheck
 }
 
 // Accept connections and pass on the channel
diff --git a/p2p/listener_test.go b/p2p/listener_test.go
index c3d33a9ae..92018e0aa 100644
--- a/p2p/listener_test.go
+++ b/p2p/listener_test.go
@@ -25,7 +25,12 @@ func TestListener(t *testing.T) {
 	}
 
 	msg := []byte("hi!")
-	go connIn.Write(msg)
+	go func() {
+		_, err := connIn.Write(msg)
+		if err != nil {
+			t.Error(err)
+		}
+	}()
 	b := make([]byte, 32)
 	n, err := connOut.Read(b)
 	if err != nil {
diff --git a/p2p/peer.go b/p2p/peer.go
index ec8349551..b0247d376 100644
--- a/p2p/peer.go
+++ b/p2p/peer.go
@@ -88,7 +88,9 @@ func newOutboundPeer(addr *NetAddress, reactorsByCh map[byte]Reactor, chDescs []
 
 	peer, err := newPeerFromConnAndConfig(conn, true, reactorsByCh, chDescs, onPeerError, ourNodePrivKey, config)
 	if err != nil {
-		conn.Close()
+		if err := conn.Close(); err != nil {
+			return nil, err
+		}
 		return nil, err
 	}
 	return peer, nil
@@ -146,7 +148,7 @@ func (p *peer) SetLogger(l log.Logger) {
 
 // CloseConn should be used when the peer was created, but never started.
 func (p *peer) CloseConn() {
-	p.conn.Close()
+	p.conn.Close() // nolint: errcheck
 }
 
 // makePersistent marks the peer as persistent.
@@ -230,7 +232,9 @@ func (p *peer) PubKey() crypto.PubKeyEd25519 {
 
 // OnStart implements BaseService.
 func (p *peer) OnStart() error {
-	p.BaseService.OnStart()
+	if err := p.BaseService.OnStart(); err != nil {
+		return err
+	}
 	_, err := p.mconn.Start()
 	return err
 }
diff --git a/p2p/peer_set_test.go b/p2p/peer_set_test.go
index e37455256..694300523 100644
--- a/p2p/peer_set_test.go
+++ b/p2p/peer_set_test.go
@@ -28,7 +28,9 @@ func TestPeerSetAddRemoveOne(t *testing.T) {
 	var peerList []Peer
 	for i := 0; i < 5; i++ {
 		p := randPeer()
-		peerSet.Add(p)
+		if err := peerSet.Add(p); err != nil {
+			t.Error(err)
+		}
 		peerList = append(peerList, p)
 	}
 
@@ -48,7 +50,9 @@ func TestPeerSetAddRemoveOne(t *testing.T) {
 	// 2. Next we are testing removing the peer at the end
 	// a) Replenish the peerSet
 	for _, peer := range peerList {
-		peerSet.Add(peer)
+		if err := peerSet.Add(peer); err != nil {
+			t.Error(err)
+		}
 	}
 
 	// b) In reverse, remove each element
diff --git a/p2p/peer_test.go b/p2p/peer_test.go
index ba52b22a4..b2a01493d 100644
--- a/p2p/peer_test.go
+++ b/p2p/peer_test.go
@@ -23,7 +23,8 @@ func TestPeerBasic(t *testing.T) {
 	p, err := createOutboundPeerAndPerformHandshake(rp.Addr(), DefaultPeerConfig())
 	require.Nil(err)
 
-	p.Start()
+	_, err = p.Start()
+	require.Nil(err)
 	defer p.Stop()
 
 	assert.True(p.IsRunning())
@@ -49,7 +50,8 @@ func TestPeerWithoutAuthEnc(t *testing.T) {
 	p, err := createOutboundPeerAndPerformHandshake(rp.Addr(), config)
 	require.Nil(err)
 
-	p.Start()
+	_, err = p.Start()
+	require.Nil(err)
 	defer p.Stop()
 
 	assert.True(p.IsRunning())
@@ -69,7 +71,9 @@ func TestPeerSend(t *testing.T) {
 	p, err := createOutboundPeerAndPerformHandshake(rp.Addr(), config)
 	require.Nil(err)
 
-	p.Start()
+	_, err = p.Start()
+	require.Nil(err)
+
 	defer p.Stop()
 
 	assert.True(p.CanSend(0x01))
@@ -78,7 +82,7 @@ func TestPeerSend(t *testing.T) {
 
 func createOutboundPeerAndPerformHandshake(addr *NetAddress, config *PeerConfig) (*peer, error) {
 	chDescs := []*ChannelDescriptor{
-		&ChannelDescriptor{ID: 0x01, Priority: 1},
+		{ID: 0x01, Priority: 1},
 	}
 	reactorsByCh := map[byte]Reactor{0x01: NewTestReactor(chDescs, true)}
 	pk := crypto.GenPrivKeyEd25519()
@@ -148,7 +152,9 @@ func (p *remotePeer) accept(l net.Listener) {
 		}
 		select {
 		case <-p.quit:
-			conn.Close()
+			if err := conn.Close(); err != nil {
+				golog.Fatal(err)
+			}
 			return
 		default:
 		}
diff --git a/p2p/pex_reactor.go b/p2p/pex_reactor.go
index fd70198f4..73bb9e75e 100644
--- a/p2p/pex_reactor.go
+++ b/p2p/pex_reactor.go
@@ -66,8 +66,13 @@ func NewPEXReactor(b *AddrBook) *PEXReactor {
 
 // OnStart implements BaseService
 func (r *PEXReactor) OnStart() error {
-	r.BaseReactor.OnStart()
-	r.book.Start()
+	if err := r.BaseReactor.OnStart(); err != nil {
+		return err
+	}
+	_, err := r.book.Start()
+	if err != nil {
+		return err
+	}
 	go r.ensurePeersRoutine()
 	go r.flushMsgCountByPeer()
 	return nil
@@ -82,7 +87,7 @@ func (r *PEXReactor) OnStop() {
 // GetChannels implements Reactor
 func (r *PEXReactor) GetChannels() []*ChannelDescriptor {
 	return []*ChannelDescriptor{
-		&ChannelDescriptor{
+		{
 			ID:                PexChannel,
 			Priority:          1,
 			SendQueueCapacity: 10,
@@ -278,7 +283,7 @@ func (r *PEXReactor) ensurePeers() {
 	// If we need more addresses, pick a random peer and ask for more.
 	if r.book.NeedMoreAddrs() {
 		if peers := r.Switch.Peers().List(); len(peers) > 0 {
-			i := rand.Int() % len(peers)
+			i := rand.Int() % len(peers) // nolint: gas
 			peer := peers[i]
 			r.Logger.Info("No addresses to dial. Sending pexRequest to random peer", "peer", peer)
 			r.RequestPEX(peer)
diff --git a/p2p/pex_reactor_test.go b/p2p/pex_reactor_test.go
index 3efc3c643..e79c73a86 100644
--- a/p2p/pex_reactor_test.go
+++ b/p2p/pex_reactor_test.go
@@ -20,7 +20,7 @@ func TestPEXReactorBasic(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "pex_reactor")
 	require.Nil(err)
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 	book := NewAddrBook(dir+"addrbook.json", true)
 	book.SetLogger(log.TestingLogger())
 
@@ -36,7 +36,7 @@ func TestPEXReactorAddRemovePeer(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "pex_reactor")
 	require.Nil(err)
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 	book := NewAddrBook(dir+"addrbook.json", true)
 	book.SetLogger(log.TestingLogger())
 
@@ -69,7 +69,7 @@ func TestPEXReactorRunning(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "pex_reactor")
 	require.Nil(err)
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 	book := NewAddrBook(dir+"addrbook.json", false)
 	book.SetLogger(log.TestingLogger())
 
@@ -139,7 +139,7 @@ func TestPEXReactorReceive(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "pex_reactor")
 	require.Nil(err)
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 	book := NewAddrBook(dir+"addrbook.json", false)
 	book.SetLogger(log.TestingLogger())
 
@@ -164,7 +164,7 @@ func TestPEXReactorAbuseFromPeer(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "pex_reactor")
 	require.Nil(err)
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 	book := NewAddrBook(dir+"addrbook.json", true)
 	book.SetLogger(log.TestingLogger())
 
diff --git a/p2p/secret_connection.go b/p2p/secret_connection.go
index 0e107ea59..aec0a7519 100644
--- a/p2p/secret_connection.go
+++ b/p2p/secret_connection.go
@@ -302,7 +302,7 @@ func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKeyEd25519, signa
 // sha256
 func hash32(input []byte) (res *[32]byte) {
 	hasher := sha256.New()
-	hasher.Write(input) // does not error
+	hasher.Write(input) // nolint: errcheck, gas
 	resSlice := hasher.Sum(nil)
 	res = new([32]byte)
 	copy(res[:], resSlice)
@@ -312,7 +312,7 @@ func hash32(input []byte) (res *[32]byte) {
 // We only fill in the first 20 bytes with ripemd160
 func hash24(input []byte) (res *[24]byte) {
 	hasher := ripemd160.New()
-	hasher.Write(input) // does not error
+	hasher.Write(input) // nolint: errcheck, gas
 	resSlice := hasher.Sum(nil)
 	res = new([24]byte)
 	copy(res[:], resSlice)
diff --git a/p2p/secret_connection_test.go b/p2p/secret_connection_test.go
index d0d008529..8b58fb417 100644
--- a/p2p/secret_connection_test.go
+++ b/p2p/secret_connection_test.go
@@ -70,8 +70,12 @@ func makeSecretConnPair(tb testing.TB) (fooSecConn, barSecConn *SecretConnection
 
 func TestSecretConnectionHandshake(t *testing.T) {
 	fooSecConn, barSecConn := makeSecretConnPair(t)
-	fooSecConn.Close()
-	barSecConn.Close()
+	if err := fooSecConn.Close(); err != nil {
+		t.Error(err)
+	}
+	if err := barSecConn.Close(); err != nil {
+		t.Error(err)
+	}
 }
 
 func TestSecretConnectionReadWrite(t *testing.T) {
@@ -110,7 +114,9 @@ func TestSecretConnectionReadWrite(t *testing.T) {
 							return
 						}
 					}
-					nodeConn.PipeWriter.Close()
+					if err := nodeConn.PipeWriter.Close(); err != nil {
+						t.Error(err)
+					}
 				},
 				func() {
 					// Node reads
@@ -125,7 +131,9 @@ func TestSecretConnectionReadWrite(t *testing.T) {
 						}
 						*nodeReads = append(*nodeReads, string(readBuffer[:n]))
 					}
-					nodeConn.PipeReader.Close()
+					if err := nodeConn.PipeReader.Close(); err != nil {
+						t.Error(err)
+					}
 				})
 		}
 	}
@@ -197,6 +205,8 @@ func BenchmarkSecretConnection(b *testing.B) {
 	}
 	b.StopTimer()
 
-	fooSecConn.Close()
+	if err := fooSecConn.Close(); err != nil {
+		b.Error(err)
+	}
 	//barSecConn.Close() race condition
 }
diff --git a/p2p/switch.go b/p2p/switch.go
index c19931550..bea2ca1bf 100644
--- a/p2p/switch.go
+++ b/p2p/switch.go
@@ -174,7 +174,9 @@ func (sw *Switch) SetNodePrivKey(nodePrivKey crypto.PrivKeyEd25519) {
 
 // OnStart implements BaseService. It starts all the reactors, peers, and listeners.
 func (sw *Switch) OnStart() error {
-	sw.BaseService.OnStart()
+	if err := sw.BaseService.OnStart(); err != nil {
+		return err
+	}
 	// Start reactors
 	for _, reactor := range sw.reactors {
 		_, err := reactor.Start()
@@ -287,7 +289,12 @@ func (sw *Switch) SetPubKeyFilter(f func(crypto.PubKeyEd25519) error) {
 }
 
 func (sw *Switch) startInitPeer(peer *peer) {
-	peer.Start() // spawn send/recv routines
+	_, err := peer.Start() // spawn send/recv routines
+	if err != nil {
+		// Should never happen
+		sw.Logger.Error("Error starting peer", "peer", peer, "err", err)
+	}
+
 	for _, reactor := range sw.reactors {
 		reactor.AddPeer(peer)
 	}
@@ -511,7 +518,7 @@ func MakeConnectedSwitches(cfg *cfg.P2PConfig, n int, initSwitch func(int, *Swit
 }
 
 // Connect2Switches will connect switches i and j via net.Pipe().
-// Blocks until a conection is established.
+// Blocks until a connection is established.
 // NOTE: caller ensures i and j are within bounds.
 func Connect2Switches(switches []*Switch, i, j int) {
 	switchI := switches[i]
@@ -568,7 +575,9 @@ func makeSwitch(cfg *cfg.P2PConfig, i int, network, version string, initSwitch f
 func (sw *Switch) addPeerWithConnection(conn net.Conn) error {
 	peer, err := newInboundPeer(conn, sw.reactorsByCh, sw.chDescs, sw.StopPeerForError, sw.nodePrivKey, sw.peerConfig)
 	if err != nil {
-		conn.Close()
+		if err := conn.Close(); err != nil {
+			sw.Logger.Error("Error closing connection", "err", err)
+		}
 		return err
 	}
 	peer.SetLogger(sw.Logger.With("peer", conn.RemoteAddr()))
@@ -583,7 +592,9 @@ func (sw *Switch) addPeerWithConnection(conn net.Conn) error {
 func (sw *Switch) addPeerWithConnectionAndConfig(conn net.Conn, config *PeerConfig) error {
 	peer, err := newInboundPeer(conn, sw.reactorsByCh, sw.chDescs, sw.StopPeerForError, sw.nodePrivKey, config)
 	if err != nil {
-		conn.Close()
+		if err := conn.Close(); err != nil {
+			sw.Logger.Error("Error closing connection", "err", err)
+		}
 		return err
 	}
 	peer.SetLogger(sw.Logger.With("peer", conn.RemoteAddr()))
diff --git a/p2p/switch_test.go b/p2p/switch_test.go
index 1ea79efef..58ef3e5f0 100644
--- a/p2p/switch_test.go
+++ b/p2p/switch_test.go
@@ -10,11 +10,12 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
 	crypto "github.com/tendermint/go-crypto"
 	wire "github.com/tendermint/go-wire"
+	"github.com/tendermint/tmlibs/log"
 
 	cfg "github.com/tendermint/tendermint/config"
-	"github.com/tendermint/tmlibs/log"
 )
 
 var (
@@ -100,12 +101,12 @@ func makeSwitchPair(t testing.TB, initSwitch func(int, *Switch) *Switch) (*Switc
 func initSwitchFunc(i int, sw *Switch) *Switch {
 	// Make two reactors of two channels each
 	sw.AddReactor("foo", NewTestReactor([]*ChannelDescriptor{
-		&ChannelDescriptor{ID: byte(0x00), Priority: 10},
-		&ChannelDescriptor{ID: byte(0x01), Priority: 10},
+		{ID: byte(0x00), Priority: 10},
+		{ID: byte(0x01), Priority: 10},
 	}, true))
 	sw.AddReactor("bar", NewTestReactor([]*ChannelDescriptor{
-		&ChannelDescriptor{ID: byte(0x02), Priority: 10},
-		&ChannelDescriptor{ID: byte(0x03), Priority: 10},
+		{ID: byte(0x02), Priority: 10},
+		{ID: byte(0x03), Priority: 10},
 	}, true))
 	return sw
 }
@@ -171,10 +172,12 @@ func TestConnAddrFilter(t *testing.T) {
 
 	// connect to good peer
 	go func() {
-		s1.addPeerWithConnection(c1)
+		err := s1.addPeerWithConnection(c1)
+		assert.NotNil(t, err, "expected err")
 	}()
 	go func() {
-		s2.addPeerWithConnection(c2)
+		err := s2.addPeerWithConnection(c2)
+		assert.NotNil(t, err, "expected err")
 	}()
 
 	assertNoPeersAfterTimeout(t, s1, 400*time.Millisecond)
@@ -206,10 +209,12 @@ func TestConnPubKeyFilter(t *testing.T) {
 
 	// connect to good peer
 	go func() {
-		s1.addPeerWithConnection(c1)
+		err := s1.addPeerWithConnection(c1)
+		assert.NotNil(t, err, "expected error")
 	}()
 	go func() {
-		s2.addPeerWithConnection(c2)
+		err := s2.addPeerWithConnection(c2)
+		assert.NotNil(t, err, "expected error")
 	}()
 
 	assertNoPeersAfterTimeout(t, s1, 400*time.Millisecond)
@@ -220,7 +225,10 @@ func TestSwitchStopsNonPersistentPeerOnError(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	sw := makeSwitch(config, 1, "testing", "123.123.123", initSwitchFunc)
-	sw.Start()
+	_, err := sw.Start()
+	if err != nil {
+		t.Error(err)
+	}
 	defer sw.Stop()
 
 	// simulate remote peer
@@ -244,7 +252,10 @@ func TestSwitchReconnectsToPersistentPeer(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	sw := makeSwitch(config, 1, "testing", "123.123.123", initSwitchFunc)
-	sw.Start()
+	_, err := sw.Start()
+	if err != nil {
+		t.Error(err)
+	}
 	defer sw.Stop()
 
 	// simulate remote peer
@@ -295,12 +306,12 @@ func BenchmarkSwitches(b *testing.B) {
 	s1, s2 := makeSwitchPair(b, func(i int, sw *Switch) *Switch {
 		// Make bar reactors of bar channels each
 		sw.AddReactor("foo", NewTestReactor([]*ChannelDescriptor{
-			&ChannelDescriptor{ID: byte(0x00), Priority: 10},
-			&ChannelDescriptor{ID: byte(0x01), Priority: 10},
+			{ID: byte(0x00), Priority: 10},
+			{ID: byte(0x01), Priority: 10},
 		}, false))
 		sw.AddReactor("bar", NewTestReactor([]*ChannelDescriptor{
-			&ChannelDescriptor{ID: byte(0x02), Priority: 10},
-			&ChannelDescriptor{ID: byte(0x03), Priority: 10},
+			{ID: byte(0x02), Priority: 10},
+			{ID: byte(0x03), Priority: 10},
 		}, false))
 		return sw
 	})
diff --git a/p2p/trust/trustmetric.go b/p2p/trust/trustmetric.go
index cbc2db7d5..c6740c0da 100644
--- a/p2p/trust/trustmetric.go
+++ b/p2p/trust/trustmetric.go
@@ -47,7 +47,9 @@ func NewTrustMetricStore(db dbm.DB, tmc TrustMetricConfig) *TrustMetricStore {
 
 // OnStart implements Service
 func (tms *TrustMetricStore) OnStart() error {
-	tms.BaseService.OnStart()
+	if err := tms.BaseService.OnStart(); err != nil {
+		return err
+	}
 
 	tms.mtx.Lock()
 	defer tms.mtx.Unlock()
diff --git a/p2p/types.go b/p2p/types.go
index 1d3770b57..4e0994b71 100644
--- a/p2p/types.go
+++ b/p2p/types.go
@@ -55,12 +55,12 @@ func (info *NodeInfo) CompatibleWith(other *NodeInfo) error {
 }
 
 func (info *NodeInfo) ListenHost() string {
-	host, _, _ := net.SplitHostPort(info.ListenAddr)
+	host, _, _ := net.SplitHostPort(info.ListenAddr) // nolint: errcheck, gas
 	return host
 }
 
 func (info *NodeInfo) ListenPort() int {
-	_, port, _ := net.SplitHostPort(info.ListenAddr)
+	_, port, _ := net.SplitHostPort(info.ListenAddr) // nolint: errcheck, gas
 	port_i, err := strconv.Atoi(port)
 	if err != nil {
 		return -1
diff --git a/p2p/upnp/probe.go b/p2p/upnp/probe.go
index 74d4d4c51..d2338b95e 100644
--- a/p2p/upnp/probe.go
+++ b/p2p/upnp/probe.go
@@ -97,11 +97,12 @@ func Probe(logger log.Logger) (caps UPNPCapabilities, err error) {
 
 	// Deferred cleanup
 	defer func() {
-		err = nat.DeletePortMapping("tcp", intPort, extPort)
-		if err != nil {
+		if err := nat.DeletePortMapping("tcp", intPort, extPort); err != nil {
 			logger.Error(cmn.Fmt("Port mapping delete error: %v", err))
 		}
-		listener.Close()
+		if err := listener.Close(); err != nil {
+			logger.Error(cmn.Fmt("Listener closing error: %v", err))
+		}
 	}()
 
 	supportsHairpin := testHairpin(listener, fmt.Sprintf("%v:%v", ext, extPort), logger)
diff --git a/p2p/upnp/upnp.go b/p2p/upnp/upnp.go
index 7d44d1e31..cac67a730 100644
--- a/p2p/upnp/upnp.go
+++ b/p2p/upnp/upnp.go
@@ -40,11 +40,10 @@ func Discover() (nat NAT, err error) {
 		return
 	}
 	socket := conn.(*net.UDPConn)
-	defer socket.Close()
+	defer socket.Close() // nolint: errcheck
 
-	err = socket.SetDeadline(time.Now().Add(3 * time.Second))
-	if err != nil {
-		return
+	if err := socket.SetDeadline(time.Now().Add(3 * time.Second)); err != nil {
+		return nil, err
 	}
 
 	st := "InternetGatewayDevice:1"
@@ -64,6 +63,9 @@ func Discover() (nat NAT, err error) {
 		}
 		var n int
 		_, _, err = socket.ReadFromUDP(answerBytes)
+		if err != nil {
+			return
+		}
 		for {
 			n, _, err = socket.ReadFromUDP(answerBytes)
 			if err != nil {
@@ -198,7 +200,8 @@ func getServiceURL(rootURL string) (url, urnDomain string, err error) {
 	if err != nil {
 		return
 	}
-	defer r.Body.Close()
+	defer r.Body.Close() // nolint: errcheck
+
 	if r.StatusCode >= 400 {
 		err = errors.New(string(r.StatusCode))
 		return
@@ -296,15 +299,21 @@ func (n *upnpNAT) getExternalIPAddress() (info statusInfo, err error) {
 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "GetExternalIPAddress", message, n.urnDomain)
 	if response != nil {
-		defer response.Body.Close()
+		defer response.Body.Close() // nolint: errcheck
 	}
 	if err != nil {
 		return
 	}
 	var envelope Envelope
 	data, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		return
+	}
 	reader := bytes.NewReader(data)
-	xml.NewDecoder(reader).Decode(&envelope)
+	err = xml.NewDecoder(reader).Decode(&envelope)
+	if err != nil {
+		return
+	}
 
 	info = statusInfo{envelope.Soap.ExternalIP.IPAddress}
 
@@ -339,7 +348,7 @@ func (n *upnpNAT) AddPortMapping(protocol string, externalPort, internalPort int
 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "AddPortMapping", message, n.urnDomain)
 	if response != nil {
-		defer response.Body.Close()
+		defer response.Body.Close() // nolint: errcheck
 	}
 	if err != nil {
 		return
@@ -365,7 +374,7 @@ func (n *upnpNAT) DeletePortMapping(protocol string, externalPort, internalPort
 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "DeletePortMapping", message, n.urnDomain)
 	if response != nil {
-		defer response.Body.Close()
+		defer response.Body.Close() // nolint: errcheck
 	}
 	if err != nil {
 		return
diff --git a/p2p/util.go b/p2p/util.go
index 2be320263..a4c3ad58b 100644
--- a/p2p/util.go
+++ b/p2p/util.go
@@ -7,9 +7,9 @@ import (
 // doubleSha256 calculates sha256(sha256(b)) and returns the resulting bytes.
 func doubleSha256(b []byte) []byte {
 	hasher := sha256.New()
-	hasher.Write(b)
+	hasher.Write(b) // nolint: errcheck, gas
 	sum := hasher.Sum(nil)
 	hasher.Reset()
-	hasher.Write(sum)
+	hasher.Write(sum) // nolint: errcheck, gas
 	return hasher.Sum(nil)
 }
diff --git a/proxy/app_conn_test.go b/proxy/app_conn_test.go
index 0c700140b..bb56d7213 100644
--- a/proxy/app_conn_test.go
+++ b/proxy/app_conn_test.go
@@ -72,7 +72,9 @@ func TestEcho(t *testing.T) {
 	for i := 0; i < 1000; i++ {
 		proxy.EchoAsync(cmn.Fmt("echo-%v", i))
 	}
-	proxy.FlushSync()
+	if err := proxy.FlushSync(); err != nil {
+		t.Error(err)
+	}
 }
 
 func BenchmarkEcho(b *testing.B) {
@@ -106,7 +108,9 @@ func BenchmarkEcho(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		proxy.EchoAsync(echoString)
 	}
-	proxy.FlushSync()
+	if err := proxy.FlushSync(); err != nil {
+		b.Error(err)
+	}
 
 	b.StopTimer()
 	// info := proxy.InfoSync(types.RequestInfo{""})
diff --git a/rpc/client/mock/abci.go b/rpc/client/mock/abci.go
index 2ed012e44..e935a2824 100644
--- a/rpc/client/mock/abci.go
+++ b/rpc/client/mock/abci.go
@@ -49,7 +49,7 @@ func (a ABCIApp) BroadcastTxAsync(tx types.Tx) (*ctypes.ResultBroadcastTx, error
 	c := a.App.CheckTx(tx)
 	// and this gets written in a background thread...
 	if c.IsOK() {
-		go func() { a.App.DeliverTx(tx) }()
+		go func() { a.App.DeliverTx(tx) }() // nolint: errcheck
 	}
 	return &ctypes.ResultBroadcastTx{c.Code, c.Data, c.Log, tx.Hash()}, nil
 }
@@ -58,7 +58,7 @@ func (a ABCIApp) BroadcastTxSync(tx types.Tx) (*ctypes.ResultBroadcastTx, error)
 	c := a.App.CheckTx(tx)
 	// and this gets written in a background thread...
 	if c.IsOK() {
-		go func() { a.App.DeliverTx(tx) }()
+		go func() { a.App.DeliverTx(tx) }() // nolint: errcheck
 	}
 	return &ctypes.ResultBroadcastTx{c.Code, c.Data, c.Log, tx.Hash()}, nil
 }
diff --git a/rpc/client/mock/abci_test.go b/rpc/client/mock/abci_test.go
index a7afa0894..36a457918 100644
--- a/rpc/client/mock/abci_test.go
+++ b/rpc/client/mock/abci_test.go
@@ -79,6 +79,8 @@ func TestABCIMock(t *testing.T) {
 
 func TestABCIRecorder(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
+
+	// This mock returns errors on everything but Query
 	m := mock.ABCIMock{
 		Info: mock.Call{Response: abci.ResponseInfo{
 			Data:    "data",
@@ -92,8 +94,11 @@ func TestABCIRecorder(t *testing.T) {
 
 	require.Equal(0, len(r.Calls))
 
-	r.ABCIInfo()
-	r.ABCIQueryWithOptions("path", data.Bytes("data"), client.ABCIQueryOptions{Trusted: false})
+	_, err := r.ABCIInfo()
+	assert.Nil(err, "expected no err on info")
+
+	_, err = r.ABCIQueryWithOptions("path", data.Bytes("data"), client.ABCIQueryOptions{Trusted: false})
+	assert.NotNil(err, "expected error on query")
 	require.Equal(2, len(r.Calls))
 
 	info := r.Calls[0]
@@ -118,11 +123,14 @@ func TestABCIRecorder(t *testing.T) {
 	assert.EqualValues("data", qa.Data)
 	assert.False(qa.Trusted)
 
-	// now add some broadcasts
+	// now add some broadcasts (should all err)
 	txs := []types.Tx{{1}, {2}, {3}}
-	r.BroadcastTxCommit(txs[0])
-	r.BroadcastTxSync(txs[1])
-	r.BroadcastTxAsync(txs[2])
+	_, err = r.BroadcastTxCommit(txs[0])
+	assert.NotNil(err, "expected err on broadcast")
+	_, err = r.BroadcastTxSync(txs[1])
+	assert.NotNil(err, "expected err on broadcast")
+	_, err = r.BroadcastTxAsync(txs[2])
+	assert.NotNil(err, "expected err on broadcast")
 
 	require.Equal(5, len(r.Calls))
 
diff --git a/rpc/client/rpc_test.go b/rpc/client/rpc_test.go
index f2626f84e..c68276354 100644
--- a/rpc/client/rpc_test.go
+++ b/rpc/client/rpc_test.go
@@ -140,7 +140,9 @@ func TestAppCalls(t *testing.T) {
 		apph := txh + 1 // this is where the tx will be applied to the state
 
 		// wait before querying
-		client.WaitForHeight(c, apph, nil)
+		if err := client.WaitForHeight(c, apph, nil); err != nil {
+			t.Error(err)
+		}
 		qres, err := c.ABCIQueryWithOptions("/key", k, client.ABCIQueryOptions{Trusted: true})
 		if assert.Nil(err) && assert.True(qres.Code.IsOK()) {
 			// assert.Equal(k, data.GetKey())  // only returned for proofs
diff --git a/rpc/core/dev.go b/rpc/core/dev.go
index a3c970d48..0b5154769 100644
--- a/rpc/core/dev.go
+++ b/rpc/core/dev.go
@@ -29,7 +29,9 @@ func UnsafeStartCPUProfiler(filename string) (*ctypes.ResultUnsafeProfile, error
 
 func UnsafeStopCPUProfiler() (*ctypes.ResultUnsafeProfile, error) {
 	pprof.StopCPUProfile()
-	profFile.Close()
+	if err := profFile.Close(); err != nil {
+		return nil, err
+	}
 	return &ctypes.ResultUnsafeProfile{}, nil
 }
 
@@ -38,8 +40,12 @@ func UnsafeWriteHeapProfile(filename string) (*ctypes.ResultUnsafeProfile, error
 	if err != nil {
 		return nil, err
 	}
-	pprof.WriteHeapProfile(memProfFile)
-	memProfFile.Close()
+	if err := pprof.WriteHeapProfile(memProfFile); err != nil {
+		return nil, err
+	}
+	if err := memProfFile.Close(); err != nil {
+		return nil, err
+	}
 
 	return &ctypes.ResultUnsafeProfile{}, nil
 }
diff --git a/rpc/grpc/client_server.go b/rpc/grpc/client_server.go
index 1c6498df7..80d736f57 100644
--- a/rpc/grpc/client_server.go
+++ b/rpc/grpc/client_server.go
@@ -25,7 +25,7 @@ func StartGRPCServer(protoAddr string) (net.Listener, error) {
 
 	grpcServer := grpc.NewServer()
 	RegisterBroadcastAPIServer(grpcServer, &broadcastAPI{})
-	go grpcServer.Serve(ln)
+	go grpcServer.Serve(ln) // nolint: errcheck
 
 	return ln, nil
 }
diff --git a/rpc/lib/client/http_client.go b/rpc/lib/client/http_client.go
index f19c2e941..a1b23a258 100644
--- a/rpc/lib/client/http_client.go
+++ b/rpc/lib/client/http_client.go
@@ -93,7 +93,8 @@ func (c *JSONRPCClient) Call(method string, params map[string]interface{}, resul
 	if err != nil {
 		return nil, err
 	}
-	defer httpResponse.Body.Close()
+	defer httpResponse.Body.Close() // nolint: errcheck
+
 	responseBytes, err := ioutil.ReadAll(httpResponse.Body)
 	if err != nil {
 		return nil, err
@@ -128,7 +129,8 @@ func (c *URIClient) Call(method string, params map[string]interface{}, result in
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
+	defer resp.Body.Close() // nolint: errcheck
+
 	responseBytes, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
diff --git a/rpc/lib/client/ws_client.go b/rpc/lib/client/ws_client.go
index bfe2272e4..573964328 100644
--- a/rpc/lib/client/ws_client.go
+++ b/rpc/lib/client/ws_client.go
@@ -290,10 +290,11 @@ func (c *WSClient) processBacklog() error {
 	select {
 	case request := <-c.backlog:
 		if c.writeWait > 0 {
-			c.conn.SetWriteDeadline(time.Now().Add(c.writeWait))
+			if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
+				c.Logger.Error("failed to set write deadline", "err", err)
+			}
 		}
-		err := c.conn.WriteJSON(request)
-		if err != nil {
+		if err := c.conn.WriteJSON(request); err != nil {
 			c.Logger.Error("failed to resend request", "err", err)
 			c.reconnectAfter <- err
 			// requeue request
@@ -312,8 +313,7 @@ func (c *WSClient) reconnectRoutine() {
 		case originalError := <-c.reconnectAfter:
 			// wait until writeRoutine and readRoutine finish
 			c.wg.Wait()
-			err := c.reconnect()
-			if err != nil {
+			if err := c.reconnect(); err != nil {
 				c.Logger.Error("failed to reconnect", "err", err, "original_err", originalError)
 				c.Stop()
 				return
@@ -352,7 +352,10 @@ func (c *WSClient) writeRoutine() {
 
 	defer func() {
 		ticker.Stop()
-		c.conn.Close()
+		if err := c.conn.Close(); err != nil {
+			// ignore error; it will trigger in tests
+			// likely because it's closing an already closed connection
+		}
 		c.wg.Done()
 	}()
 
@@ -360,10 +363,11 @@ func (c *WSClient) writeRoutine() {
 		select {
 		case request := <-c.send:
 			if c.writeWait > 0 {
-				c.conn.SetWriteDeadline(time.Now().Add(c.writeWait))
+				if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
+					c.Logger.Error("failed to set write deadline", "err", err)
+				}
 			}
-			err := c.conn.WriteJSON(request)
-			if err != nil {
+			if err := c.conn.WriteJSON(request); err != nil {
 				c.Logger.Error("failed to send request", "err", err)
 				c.reconnectAfter <- err
 				// add request to the backlog, so we don't lose it
@@ -372,10 +376,11 @@ func (c *WSClient) writeRoutine() {
 			}
 		case <-ticker.C:
 			if c.writeWait > 0 {
-				c.conn.SetWriteDeadline(time.Now().Add(c.writeWait))
+				if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
+					c.Logger.Error("failed to set write deadline", "err", err)
+				}
 			}
-			err := c.conn.WriteMessage(websocket.PingMessage, []byte{})
-			if err != nil {
+			if err := c.conn.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
 				c.Logger.Error("failed to write ping", "err", err)
 				c.reconnectAfter <- err
 				return
@@ -387,7 +392,9 @@ func (c *WSClient) writeRoutine() {
 		case <-c.readRoutineQuit:
 			return
 		case <-c.Quit:
-			c.conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
+			if err := c.conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")); err != nil {
+				c.Logger.Error("failed to write message", "err", err)
+			}
 			return
 		}
 	}
@@ -397,7 +404,10 @@ func (c *WSClient) writeRoutine() {
 // executing all reads from this goroutine.
 func (c *WSClient) readRoutine() {
 	defer func() {
-		c.conn.Close()
+		if err := c.conn.Close(); err != nil {
+			// ignore error; it will trigger in tests
+			// likely because it's closing an already closed connection
+		}
 		c.wg.Done()
 	}()
 
@@ -415,7 +425,9 @@ func (c *WSClient) readRoutine() {
 	for {
 		// reset deadline for every message type (control or data)
 		if c.readWait > 0 {
-			c.conn.SetReadDeadline(time.Now().Add(c.readWait))
+			if err := c.conn.SetReadDeadline(time.Now().Add(c.readWait)); err != nil {
+				c.Logger.Error("failed to set read deadline", "err", err)
+			}
 		}
 		_, data, err := c.conn.ReadMessage()
 		if err != nil {
diff --git a/rpc/lib/client/ws_client_test.go b/rpc/lib/client/ws_client_test.go
index 3a0632e38..8552a4ee1 100644
--- a/rpc/lib/client/ws_client_test.go
+++ b/rpc/lib/client/ws_client_test.go
@@ -34,7 +34,7 @@ func (h *myHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		panic(err)
 	}
-	defer conn.Close()
+	defer conn.Close() // nolint: errcheck
 	for {
 		messageType, _, err := conn.ReadMessage()
 		if err != nil {
@@ -43,7 +43,9 @@ func (h *myHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 		h.mtx.RLock()
 		if h.closeConnAfterRead {
-			conn.Close()
+			if err := conn.Close(); err != nil {
+				panic(err)
+			}
 		}
 		h.mtx.RUnlock()
 
@@ -102,7 +104,9 @@ func TestWSClientReconnectsAfterWriteFailure(t *testing.T) {
 	go callWgDoneOnResult(t, c, &wg)
 
 	// hacky way to abort the connection before write
-	c.conn.Close()
+	if err := c.conn.Close(); err != nil {
+		t.Error(err)
+	}
 
 	// results in WS write error, the client should resend on reconnect
 	call(t, "a", c)
@@ -135,14 +139,18 @@ func TestWSClientReconnectFailure(t *testing.T) {
 	}()
 
 	// hacky way to abort the connection before write
-	c.conn.Close()
+	if err := c.conn.Close(); err != nil {
+		t.Error(err)
+	}
 	s.Close()
 
 	// results in WS write error
 	// provide timeout to avoid blocking
 	ctx, cancel := context.WithTimeout(context.Background(), wsCallTimeout)
 	defer cancel()
-	c.Call(ctx, "a", make(map[string]interface{}))
+	if err := c.Call(ctx, "a", make(map[string]interface{})); err != nil {
+		t.Error(err)
+	}
 
 	// expect to reconnect almost immediately
 	time.Sleep(10 * time.Millisecond)
diff --git a/rpc/lib/rpc_test.go b/rpc/lib/rpc_test.go
index b5af0e43a..433041c1f 100644
--- a/rpc/lib/rpc_test.go
+++ b/rpc/lib/rpc_test.go
@@ -216,19 +216,17 @@ func echoViaWS(cl *client.WSClient, val string) (string, error) {
 		return "", err
 	}
 
-	select {
-	case msg := <-cl.ResponsesCh:
-		if msg.Error != nil {
-			return "", err
+	msg := <-cl.ResponsesCh
+	if msg.Error != nil {
+		return "", err
 
-		}
-		result := new(ResultEcho)
-		err = json.Unmarshal(msg.Result, result)
-		if err != nil {
-			return "", nil
-		}
-		return result.Value, nil
 	}
+	result := new(ResultEcho)
+	err = json.Unmarshal(msg.Result, result)
+	if err != nil {
+		return "", nil
+	}
+	return result.Value, nil
 }
 
 func echoBytesViaWS(cl *client.WSClient, bytes []byte) ([]byte, error) {
@@ -240,19 +238,17 @@ func echoBytesViaWS(cl *client.WSClient, bytes []byte) ([]byte, error) {
 		return []byte{}, err
 	}
 
-	select {
-	case msg := <-cl.ResponsesCh:
-		if msg.Error != nil {
-			return []byte{}, msg.Error
+	msg := <-cl.ResponsesCh
+	if msg.Error != nil {
+		return []byte{}, msg.Error
 
-		}
-		result := new(ResultEchoBytes)
-		err = json.Unmarshal(msg.Result, result)
-		if err != nil {
-			return []byte{}, nil
-		}
-		return result.Value, nil
 	}
+	result := new(ResultEchoBytes)
+	err = json.Unmarshal(msg.Result, result)
+	if err != nil {
+		return []byte{}, nil
+	}
+	return result.Value, nil
 }
 
 func testWithWSClient(t *testing.T, cl *client.WSClient) {
@@ -322,17 +318,15 @@ func TestWSNewWSRPCFunc(t *testing.T) {
 	err = cl.Call(context.Background(), "echo_ws", params)
 	require.Nil(t, err)
 
-	select {
-	case msg := <-cl.ResponsesCh:
-		if msg.Error != nil {
-			t.Fatal(err)
-		}
-		result := new(ResultEcho)
-		err = json.Unmarshal(msg.Result, result)
-		require.Nil(t, err)
-		got := result.Value
-		assert.Equal(t, got, val)
+	msg := <-cl.ResponsesCh
+	if msg.Error != nil {
+		t.Fatal(err)
 	}
+	result := new(ResultEcho)
+	err = json.Unmarshal(msg.Result, result)
+	require.Nil(t, err)
+	got := result.Value
+	assert.Equal(t, got, val)
 }
 
 func TestWSHandlesArrayParams(t *testing.T) {
@@ -347,17 +341,15 @@ func TestWSHandlesArrayParams(t *testing.T) {
 	err = cl.CallWithArrayParams(context.Background(), "echo_ws", params)
 	require.Nil(t, err)
 
-	select {
-	case msg := <-cl.ResponsesCh:
-		if msg.Error != nil {
-			t.Fatalf("%+v", err)
-		}
-		result := new(ResultEcho)
-		err = json.Unmarshal(msg.Result, result)
-		require.Nil(t, err)
-		got := result.Value
-		assert.Equal(t, got, val)
+	msg := <-cl.ResponsesCh
+	if msg.Error != nil {
+		t.Fatalf("%+v", err)
 	}
+	result := new(ResultEcho)
+	err = json.Unmarshal(msg.Result, result)
+	require.Nil(t, err)
+	got := result.Value
+	assert.Equal(t, got, val)
 }
 
 // TestWSClientPingPong checks that a client & server exchange pings
diff --git a/rpc/lib/server/handlers.go b/rpc/lib/server/handlers.go
index 1f2907001..2e24195dc 100644
--- a/rpc/lib/server/handlers.go
+++ b/rpc/lib/server/handlers.go
@@ -99,7 +99,11 @@ func funcReturnTypes(f interface{}) []reflect.Type {
 // jsonrpc calls grab the given method's function info and runs reflect.Call
 func makeJSONRPCHandler(funcMap map[string]*RPCFunc, logger log.Logger) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		b, _ := ioutil.ReadAll(r.Body)
+		b, err := ioutil.ReadAll(r.Body)
+		if err != nil {
+			WriteRPCResponseHTTP(w, types.RPCInvalidRequestError("", errors.Wrap(err, "Error reading request body")))
+			return
+		}
 		// if its an empty request (like from a browser),
 		// just display a list of functions
 		if len(b) == 0 {
@@ -108,7 +112,7 @@ func makeJSONRPCHandler(funcMap map[string]*RPCFunc, logger log.Logger) http.Han
 		}
 
 		var request types.RPCRequest
-		err := json.Unmarshal(b, &request)
+		err = json.Unmarshal(b, &request)
 		if err != nil {
 			WriteRPCResponseHTTP(w, types.RPCParseError("", errors.Wrap(err, "Error unmarshalling request")))
 			return
@@ -529,7 +533,7 @@ func (wsc *wsConnection) readRoutine() {
 			wsc.WriteRPCResponse(types.RPCInternalError("unknown", err))
 			go wsc.readRoutine()
 		} else {
-			wsc.baseConn.Close()
+			wsc.baseConn.Close() // nolint: errcheck
 		}
 	}()
 
@@ -543,7 +547,9 @@ func (wsc *wsConnection) readRoutine() {
 			return
 		default:
 			// reset deadline for every type of message (control or data)
-			wsc.baseConn.SetReadDeadline(time.Now().Add(wsc.readWait))
+			if err := wsc.baseConn.SetReadDeadline(time.Now().Add(wsc.readWait)); err != nil {
+				wsc.Logger.Error("failed to set read deadline", "err", err)
+			}
 			var in []byte
 			_, in, err := wsc.baseConn.ReadMessage()
 			if err != nil {
@@ -615,7 +621,9 @@ func (wsc *wsConnection) writeRoutine() {
 	pingTicker := time.NewTicker(wsc.pingPeriod)
 	defer func() {
 		pingTicker.Stop()
-		wsc.baseConn.Close()
+		if err := wsc.baseConn.Close(); err != nil {
+			wsc.Logger.Error("Error closing connection", "err", err)
+		}
 	}()
 
 	// https://github.com/gorilla/websocket/issues/97
@@ -662,7 +670,9 @@ func (wsc *wsConnection) writeRoutine() {
 // All writes to the websocket must (re)set the write deadline.
 // If some writes don't set it while others do, they may timeout incorrectly (https://github.com/tendermint/tendermint/issues/553)
 func (wsc *wsConnection) writeMessageWithDeadline(msgType int, msg []byte) error {
-	wsc.baseConn.SetWriteDeadline(time.Now().Add(wsc.writeWait))
+	if err := wsc.baseConn.SetWriteDeadline(time.Now().Add(wsc.writeWait)); err != nil {
+		return err
+	}
 	return wsc.baseConn.WriteMessage(msgType, msg)
 }
 
@@ -713,7 +723,10 @@ func (wm *WebsocketManager) WebsocketHandler(w http.ResponseWriter, r *http.Requ
 	con := NewWSConnection(wsConn, wm.funcMap, wm.wsConnOptions...)
 	con.SetLogger(wm.logger.With("remote", wsConn.RemoteAddr()))
 	wm.logger.Info("New websocket connection", "remote", con.remoteAddr)
-	con.Start() // Blocking
+	_, err = con.Start() // Blocking
+	if err != nil {
+		wm.logger.Error("Error starting connection", "err", err)
+	}
 }
 
 // rpc.websocket
@@ -770,5 +783,5 @@ func writeListOfEndpoints(w http.ResponseWriter, r *http.Request, funcMap map[st
 	buf.WriteString("</body></html>")
 	w.Header().Set("Content-Type", "text/html")
 	w.WriteHeader(200)
-	w.Write(buf.Bytes())
+	w.Write(buf.Bytes()) // nolint: errcheck
 }
diff --git a/rpc/lib/server/http_server.go b/rpc/lib/server/http_server.go
index 7623337db..515baf5dd 100644
--- a/rpc/lib/server/http_server.go
+++ b/rpc/lib/server/http_server.go
@@ -56,7 +56,7 @@ func WriteRPCResponseHTTPError(w http.ResponseWriter, httpCode int, res types.RP
 
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(httpCode)
-	w.Write(jsonBytes)
+	w.Write(jsonBytes) // nolint: errcheck, gas
 }
 
 func WriteRPCResponseHTTP(w http.ResponseWriter, res types.RPCResponse) {
@@ -66,7 +66,7 @@ func WriteRPCResponseHTTP(w http.ResponseWriter, res types.RPCResponse) {
 	}
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(200)
-	w.Write(jsonBytes)
+	w.Write(jsonBytes) // nolint: errcheck, gas
 }
 
 //-----------------------------------------------------------------------------
diff --git a/rpc/lib/server/parse_test.go b/rpc/lib/server/parse_test.go
index 3c6d6edde..a86226f2c 100644
--- a/rpc/lib/server/parse_test.go
+++ b/rpc/lib/server/parse_test.go
@@ -150,7 +150,7 @@ func TestParseRPC(t *testing.T) {
 		{`{"name": "john", "height": 22}`, 22, "john", false},
 		// defaults
 		{`{"name": "solo", "unused": "stuff"}`, 0, "solo", false},
-		// should fail - wrong types/lenght
+		// should fail - wrong types/length
 		{`["flew", 7]`, 0, "", true},
 		{`[7,"flew",100]`, 0, "", true},
 		{`{"name": -12, "height": "fred"}`, 0, "", true},
diff --git a/rpc/test/helpers.go b/rpc/test/helpers.go
index 03538b512..d7e5f82ca 100644
--- a/rpc/test/helpers.go
+++ b/rpc/test/helpers.go
@@ -92,7 +92,10 @@ func GetGRPCClient() core_grpc.BroadcastAPIClient {
 // StartTendermint starts a test tendermint server in a go routine and returns when it is initialized
 func StartTendermint(app abci.Application) *nm.Node {
 	node := NewTendermint(app)
-	node.Start()
+	_, err := node.Start()
+	if err != nil {
+		panic(err)
+	}
 
 	// wait for rpc
 	waitForRPC()
diff --git a/scripts/wal2json/main.go b/scripts/wal2json/main.go
index 2cf40c57d..e44ed4b17 100644
--- a/scripts/wal2json/main.go
+++ b/scripts/wal2json/main.go
@@ -41,10 +41,18 @@ func main() {
 			panic(fmt.Errorf("failed to marshal msg: %v", err))
 		}
 
-		os.Stdout.Write(json)
-		os.Stdout.Write([]byte("\n"))
-		if end, ok := msg.Msg.(cs.EndHeightMessage); ok {
-			os.Stdout.Write([]byte(fmt.Sprintf("ENDHEIGHT %d\n", end.Height)))
+		_, err = os.Stdout.Write(json)
+		if err == nil {
+			_, err = os.Stdout.Write([]byte("\n"))
+		}
+		if err == nil {
+			if end, ok := msg.Msg.(cs.EndHeightMessage); ok {
+				_, err = os.Stdout.Write([]byte(fmt.Sprintf("ENDHEIGHT %d\n", end.Height))) // nolint: errcheck, gas
+			}
+		}
+		if err != nil {
+			fmt.Println("Failed to write message", err)
+			os.Exit(1)
 		}
 	}
 }
diff --git a/state/execution.go b/state/execution.go
index 76205d0fd..6c74f7a9e 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -160,6 +160,7 @@ func updateValidators(validators *types.ValidatorSet, changedValidators []*abci.
 
 // return a bit array of validators that signed the last commit
 // NOTE: assumes commits have already been authenticated
+/* function is currently unused
 func commitBitArrayFromBlock(block *types.Block) *cmn.BitArray {
 	signed := cmn.NewBitArray(len(block.LastCommit.Precommits))
 	for i, precommit := range block.LastCommit.Precommits {
@@ -169,6 +170,7 @@ func commitBitArrayFromBlock(block *types.Block) *cmn.BitArray {
 	}
 	return signed
 }
+*/
 
 //-----------------------------------------------------
 // Validate block
@@ -271,9 +273,7 @@ func (s *State) CommitStateUpdateMempool(proxyAppConn proxy.AppConnConsensus, bl
 	s.AppHash = res.Data
 
 	// Update mempool.
-	mempool.Update(block.Height, block.Txs)
-
-	return nil
+	return mempool.Update(block.Height, block.Txs)
 }
 
 func (s *State) indexTxs(abciResponses *ABCIResponses) {
@@ -282,14 +282,18 @@ func (s *State) indexTxs(abciResponses *ABCIResponses) {
 	batch := txindex.NewBatch(len(abciResponses.DeliverTx))
 	for i, d := range abciResponses.DeliverTx {
 		tx := abciResponses.txs[i]
-		batch.Add(types.TxResult{
+		if err := batch.Add(types.TxResult{
 			Height: uint64(abciResponses.Height),
 			Index:  uint32(i),
 			Tx:     tx,
 			Result: *d,
-		})
+		}); err != nil {
+			s.logger.Error("Error with batch.Add", "err", err)
+		}
+	}
+	if err := s.TxIndexer.AddBatch(batch); err != nil {
+		s.logger.Error("Error adding batch", "err", err)
 	}
-	s.TxIndexer.AddBatch(batch)
 }
 
 // ExecCommitBlock executes and commits a block on the proxyApp without validating or mutating the state.
diff --git a/state/execution_test.go b/state/execution_test.go
index 8fcdcf1c5..626b2ecde 100644
--- a/state/execution_test.go
+++ b/state/execution_test.go
@@ -59,7 +59,7 @@ func state() *State {
 	s, _ := MakeGenesisState(dbm.NewMemDB(), &types.GenesisDoc{
 		ChainID: chainID,
 		Validators: []types.GenesisValidator{
-			types.GenesisValidator{privKey.PubKey(), 10000, "test"},
+			{privKey.PubKey(), 10000, "test"},
 		},
 		AppHash: nil,
 	})
diff --git a/state/txindex/indexer.go b/state/txindex/indexer.go
index 66897905c..039460a16 100644
--- a/state/txindex/indexer.go
+++ b/state/txindex/indexer.go
@@ -11,7 +11,7 @@ type TxIndexer interface {
 
 	// AddBatch analyzes, indexes or stores a batch of transactions.
 	// NOTE: We do not specify Index method for analyzing a single transaction
-	// here because it bears heavy perfomance loses. Almost all advanced indexers
+	// here because it bears heavy performance losses. Almost all advanced indexers
 	// support batching.
 	AddBatch(b *Batch) error
 
diff --git a/state/txindex/kv/kv_test.go b/state/txindex/kv/kv_test.go
index 903189c2b..673674b30 100644
--- a/state/txindex/kv/kv_test.go
+++ b/state/txindex/kv/kv_test.go
@@ -21,7 +21,9 @@ func TestTxIndex(t *testing.T) {
 	hash := tx.Hash()
 
 	batch := txindex.NewBatch(1)
-	batch.Add(*txResult)
+	if err := batch.Add(*txResult); err != nil {
+		t.Error(err)
+	}
 	err := indexer.AddBatch(batch)
 	require.Nil(t, err)
 
@@ -38,14 +40,16 @@ func benchmarkTxIndex(txsCount int, b *testing.B) {
 	if err != nil {
 		b.Fatal(err)
 	}
-	defer os.RemoveAll(dir)
+	defer os.RemoveAll(dir) // nolint: errcheck
 
 	store := db.NewDB("tx_index", "leveldb", dir)
 	indexer := &TxIndex{store: store}
 
 	batch := txindex.NewBatch(txsCount)
 	for i := 0; i < txsCount; i++ {
-		batch.Add(*txResult)
+		if err := batch.Add(*txResult); err != nil {
+			b.Fatal(err)
+		}
 		txResult.Index += 1
 	}
 
diff --git a/test/run_test.sh b/test/run_test.sh
index 6e4823f10..cecd2c72b 100644
--- a/test/run_test.sh
+++ b/test/run_test.sh
@@ -6,6 +6,10 @@ pwd
 BRANCH=$(git rev-parse --abbrev-ref HEAD)
 echo "Current branch: $BRANCH"
 
+# run the linter
+# TODO: drop the `_test` once we're ballin' enough
+make metalinter_test
+
 # run the go unit tests with coverage
 bash test/test_cover.sh
 
diff --git a/types/heartbeat_test.go b/types/heartbeat_test.go
index 8a0967128..660ccd0f9 100644
--- a/types/heartbeat_test.go
+++ b/types/heartbeat_test.go
@@ -40,17 +40,17 @@ func TestHeartbeatWriteSignBytes(t *testing.T) {
 
 	hb := &Heartbeat{ValidatorIndex: 1, Height: 10, Round: 1}
 	hb.WriteSignBytes("0xdeadbeef", buf, &n, &err)
-	require.Equal(t, string(buf.Bytes()), `{"chain_id":"0xdeadbeef","heartbeat":{"height":10,"round":1,"sequence":0,"validator_address":"","validator_index":1}}`)
+	require.Equal(t, buf.String(), `{"chain_id":"0xdeadbeef","heartbeat":{"height":10,"round":1,"sequence":0,"validator_address":"","validator_index":1}}`)
 
 	buf.Reset()
 	plainHb := &Heartbeat{}
 	plainHb.WriteSignBytes("0xdeadbeef", buf, &n, &err)
-	require.Equal(t, string(buf.Bytes()), `{"chain_id":"0xdeadbeef","heartbeat":{"height":0,"round":0,"sequence":0,"validator_address":"","validator_index":0}}`)
+	require.Equal(t, buf.String(), `{"chain_id":"0xdeadbeef","heartbeat":{"height":0,"round":0,"sequence":0,"validator_address":"","validator_index":0}}`)
 
 	require.Panics(t, func() {
 		buf.Reset()
 		var nilHb *Heartbeat
 		nilHb.WriteSignBytes("0xdeadbeef", buf, &n, &err)
-		require.Equal(t, string(buf.Bytes()), "null")
+		require.Equal(t, buf.String(), "null")
 	})
 }
diff --git a/types/part_set.go b/types/part_set.go
index e15d2cab6..e8a0997c0 100644
--- a/types/part_set.go
+++ b/types/part_set.go
@@ -34,7 +34,7 @@ func (part *Part) Hash() []byte {
 		return part.hash
 	} else {
 		hasher := ripemd160.New()
-		hasher.Write(part.Bytes) // doesn't err
+		hasher.Write(part.Bytes) // nolint: errcheck, gas
 		part.hash = hasher.Sum(nil)
 		return part.hash
 	}
diff --git a/types/priv_validator_test.go b/types/priv_validator_test.go
index ac91de861..cd2dfc137 100644
--- a/types/priv_validator_test.go
+++ b/types/priv_validator_test.go
@@ -34,7 +34,9 @@ func TestLoadOrGenValidator(t *testing.T) {
 	assert := assert.New(t)
 
 	_, tempFilePath := cmn.Tempfile("priv_validator_")
-	os.Remove(tempFilePath)
+	if err := os.Remove(tempFilePath); err != nil {
+		t.Error(err)
+	}
 	privVal := LoadOrGenPrivValidatorFS(tempFilePath)
 	addr := privVal.GetAddress()
 	privVal = LoadOrGenPrivValidatorFS(tempFilePath)
diff --git a/types/proposal_test.go b/types/proposal_test.go
index d1c991849..352ba8de1 100644
--- a/types/proposal_test.go
+++ b/types/proposal_test.go
@@ -30,7 +30,10 @@ func BenchmarkProposalWriteSignBytes(b *testing.B) {
 func BenchmarkProposalSign(b *testing.B) {
 	privVal := GenPrivValidatorFS("")
 	for i := 0; i < b.N; i++ {
-		privVal.Signer.Sign(SignBytes("test_chain_id", testProposal))
+		_, err := privVal.Signer.Sign(SignBytes("test_chain_id", testProposal))
+		if err != nil {
+			b.Error(err)
+		}
 	}
 }
 
diff --git a/types/services.go b/types/services.go
index e34d846b5..f025de79b 100644
--- a/types/services.go
+++ b/types/services.go
@@ -25,7 +25,7 @@ type Mempool interface {
 	Size() int
 	CheckTx(Tx, func(*abci.Response)) error
 	Reap(int) Txs
-	Update(height int, txs Txs)
+	Update(height int, txs Txs) error
 	Flush()
 
 	TxsAvailable() <-chan int
@@ -42,7 +42,7 @@ func (m MockMempool) Unlock()                                      {}
 func (m MockMempool) Size() int                                    { return 0 }
 func (m MockMempool) CheckTx(tx Tx, cb func(*abci.Response)) error { return nil }
 func (m MockMempool) Reap(n int) Txs                               { return Txs{} }
-func (m MockMempool) Update(height int, txs Txs)                   {}
+func (m MockMempool) Update(height int, txs Txs) error             { return nil }
 func (m MockMempool) Flush()                                       {}
 func (m MockMempool) TxsAvailable() <-chan int                     { return make(chan int) }
 func (m MockMempool) EnableTxsAvailable()                          {}
diff --git a/types/validator.go b/types/validator.go
index 7b167b273..c5d064e01 100644
--- a/types/validator.go
+++ b/types/validator.go
@@ -71,7 +71,7 @@ func (v *Validator) String() string {
 }
 
 // Hash computes the unique ID of a validator with a given voting power.
-// It exludes the Accum value, which changes with every round.
+// It excludes the Accum value, which changes with every round.
 func (v *Validator) Hash() []byte {
 	return wire.BinaryRipemd160(struct {
 		Address     data.Bytes
diff --git a/types/validator_set_test.go b/types/validator_set_test.go
index a285adeeb..572b7b007 100644
--- a/types/validator_set_test.go
+++ b/types/validator_set_test.go
@@ -6,7 +6,7 @@ import (
 	"testing"
 
 	"github.com/tendermint/go-crypto"
-	wire "github.com/tendermint/go-wire"
+	"github.com/tendermint/go-wire"
 	cmn "github.com/tendermint/tmlibs/common"
 )
 
diff --git a/types/vote_set_test.go b/types/vote_set_test.go
index 5a757a00b..ebead3eea 100644
--- a/types/vote_set_test.go
+++ b/types/vote_set_test.go
@@ -126,7 +126,10 @@ func Test2_3Majority(t *testing.T) {
 	// 6 out of 10 voted for nil.
 	for i := 0; i < 6; i++ {
 		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
-		signAddVote(privValidators[i], vote, voteSet)
+		_, err := signAddVote(privValidators[i], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 	}
 	blockID, ok := voteSet.TwoThirdsMajority()
 	if ok || !blockID.IsZero() {
@@ -136,7 +139,10 @@ func Test2_3Majority(t *testing.T) {
 	// 7th validator voted for some blockhash
 	{
 		vote := withValidator(voteProto, privValidators[6].GetAddress(), 6)
-		signAddVote(privValidators[6], withBlockHash(vote, cmn.RandBytes(32)), voteSet)
+		_, err := signAddVote(privValidators[6], withBlockHash(vote, cmn.RandBytes(32)), voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority")
@@ -146,7 +152,10 @@ func Test2_3Majority(t *testing.T) {
 	// 8th validator voted for nil.
 	{
 		vote := withValidator(voteProto, privValidators[7].GetAddress(), 7)
-		signAddVote(privValidators[7], vote, voteSet)
+		_, err := signAddVote(privValidators[7], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if !ok || !blockID.IsZero() {
 			t.Errorf("There should be 2/3 majority for nil")
@@ -174,7 +183,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	// 66 out of 100 voted for nil.
 	for i := 0; i < 66; i++ {
 		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
-		signAddVote(privValidators[i], vote, voteSet)
+		_, err := signAddVote(privValidators[i], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 	}
 	blockID, ok := voteSet.TwoThirdsMajority()
 	if ok || !blockID.IsZero() {
@@ -184,7 +196,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	// 67th validator voted for nil
 	{
 		vote := withValidator(voteProto, privValidators[66].GetAddress(), 66)
-		signAddVote(privValidators[66], withBlockHash(vote, nil), voteSet)
+		_, err := signAddVote(privValidators[66], withBlockHash(vote, nil), voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added was nil")
@@ -195,7 +210,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	{
 		vote := withValidator(voteProto, privValidators[67].GetAddress(), 67)
 		blockPartsHeader := PartSetHeader{blockPartsTotal, crypto.CRandBytes(32)}
-		signAddVote(privValidators[67], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
+		_, err := signAddVote(privValidators[67], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different PartSetHeader Hash")
@@ -206,7 +224,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	{
 		vote := withValidator(voteProto, privValidators[68].GetAddress(), 68)
 		blockPartsHeader := PartSetHeader{blockPartsTotal + 1, blockPartsHeader.Hash}
-		signAddVote(privValidators[68], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
+		_, err := signAddVote(privValidators[68], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different PartSetHeader Total")
@@ -216,7 +237,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	// 70th validator voted for different BlockHash
 	{
 		vote := withValidator(voteProto, privValidators[69].GetAddress(), 69)
-		signAddVote(privValidators[69], withBlockHash(vote, cmn.RandBytes(32)), voteSet)
+		_, err := signAddVote(privValidators[69], withBlockHash(vote, cmn.RandBytes(32)), voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different BlockHash")
@@ -226,7 +250,10 @@ func Test2_3MajorityRedux(t *testing.T) {
 	// 71st validator voted for the right BlockHash & BlockPartsHeader
 	{
 		vote := withValidator(voteProto, privValidators[70].GetAddress(), 70)
-		signAddVote(privValidators[70], vote, voteSet)
+		_, err := signAddVote(privValidators[70], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if !ok || !blockID.Equals(BlockID{blockHash, blockPartsHeader}) {
 			t.Errorf("There should be 2/3 majority")
@@ -439,7 +466,10 @@ func TestMakeCommit(t *testing.T) {
 	// 6 out of 10 voted for some block.
 	for i := 0; i < 6; i++ {
 		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
-		signAddVote(privValidators[i], vote, voteSet)
+		_, err := signAddVote(privValidators[i], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 	}
 
 	// MakeCommit should fail.
@@ -450,13 +480,20 @@ func TestMakeCommit(t *testing.T) {
 		vote := withValidator(voteProto, privValidators[6].GetAddress(), 6)
 		vote = withBlockHash(vote, cmn.RandBytes(32))
 		vote = withBlockPartsHeader(vote, PartSetHeader{123, cmn.RandBytes(32)})
-		signAddVote(privValidators[6], vote, voteSet)
+
+		_, err := signAddVote(privValidators[6], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 	}
 
 	// The 8th voted like everyone else.
 	{
 		vote := withValidator(voteProto, privValidators[7].GetAddress(), 7)
-		signAddVote(privValidators[7], vote, voteSet)
+		_, err := signAddVote(privValidators[7], vote, voteSet)
+		if err != nil {
+			t.Error(err)
+		}
 	}
 
 	commit := voteSet.MakeCommit()