code: func (t Time) MarshalJSON() ([]byte, error) {
  	if t.IsZero() {
  		// Encode unset/nil objects as JSON's "null".
  		return []byte("null"), nil
  	}
  	buf := make([]byte, 0, len(time.RFC3339)+2)
  	buf = append(buf, '"')
  	// time cannot contain non escapable JSON characters
  	buf = t.UTC().AppendFormat(buf, time.RFC3339)
  	buf = append(buf, '"')
  	return buf, nil
  }
docs: // MarshalJSON implements the json.Marshaler interface.