code: func MustGet(key string) (string, error) {
  	gil.RLock()
  	defer gil.RUnlock()
  	if v, ok := env[key]; ok {
  		return v, nil
  	}
  	return "", fmt.Errorf("could not find ENV var with %s", key)
  }
docs: // Get a value from the ENV. If it doesn't exist
  // an error will be returned