code: func HandleCommand(helper Helper, key string, in io.Reader, out io.Writer) error {
  	switch key {
  	case "store":
  		return Store(helper, in)
  	case "get":
  		return Get(helper, in, out)
  	case "erase":
  		return Erase(helper, in)
  	case "list":
  		return List(helper, out)
  	case "version":
  		return PrintVersion(out)
  	}
  	return fmt.Errorf("Unknown credential action `%s`", key)
  }
docs: // HandleCommand uses a helper and a key to run a credential action.