Switch to Go environment and add extra sanity check.
Switch to Go environment and add extra sanity check.

Add notes on why Go is removed and final sanity check to ensure that
it is not present.

m3db/prometheus_client_golang,telendt/client_golang,fabxc/client_golang,mattkanwisher/client_golang,asbjornenge/client_golang,prometheus/client_golang,stapelberg/client_golang,jimmidyson/prometheus-client_golang,KevinPike/client_golang