code: func GetGoVars() (string, string, error) {
  	gopath := os.Getenv("GOPATH")
  	if gopath == "" {
  		return "", "", errors.New("Please set the $GOPATH environment variable")
  	}
  
  	goroot := filepath.Clean(runtime.GOROOT())
  	if goroot == "" {
  		return "", "", errors.New("Please set $GOROOT environment variable")
  	}
  
  	return gopath, goroot, nil
  }
docs: // return gopath, goroot, err