code: func (ts *Timestamp) UnmarshalJSON(b []byte) error {
  	var j string
  	err := json.Unmarshal(b, &j)
  	if err == nil {
  		tsp, err := TimestampParse(string(j))
  		if err == nil {
  			*ts = tsp
  		}
  	}
  	return err
  }
docs: //
  // UnmarshalJSON - parse a Timestamp from a JSON string
  //