Add GO111MODULE=auto to GO_PKG_BUILD_VARS to allow the package to be
built in non-module mode.

Module-aware mode will be mandatory in the next golang release.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

tor-fw-helper is a helper to automatically configuring port forwarding
for tor, using UPnP or NAT-PMP NAT traversal.

This is a tor-fw-helper rewrite in Go that functions as a drop in
replacement for the original C code.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>