gc not honoring path from configuration

[brosner]

In an attempt to work around https://github.com/atom/atom-shell/issues/550 causing issues for atom-lint, I found that the Go plugin fails to honor the configuration path. In my configuration I have:

'gc':
  'path': '/usr/local/bin/go'

However, the getEnv function in the Go plugin doesn't use this path when it calls go env.