Export required env vars for Go toolchain.

entrypoint.sh

@@ -6,6 +6,11 @@ CMD=$*
 # Just ensure we have PATH defined properly.
 PATH="${PATH}:/usr/bin/:/usr/sbin/:/bin/:/usr/local/bin/:/opt/bin/"
 
+# Also make sure that Go's environment variables are set.
+export GOCACHE=/home/container/go/build
+export GOMODCACHE=/home/container/go/pkg/mod
+export GOPATH=/home/container/go
+
 if [ "${CMD}" == "" ]; then
     CMD="${INPUT_COMMAND}"
 fi