code: func (t *Timestamp) UnmarshalJSON(b []byte) error {
  	// Ignore null, like in the main JSON package.
  	if string(b) == "null" {
  		return nil
  	}
  	var err error
  	t.Time, err = time.Parse(`"`+timeLayout+`"`, string(b))
  	return err
  }
docs: // UnmarshalJSON implements the json.Unmarshaler interface.
  // The time is expected to be a quoted string in Gerrit's timestamp format.