code: func (t *Time) MarshalJSON() ([]byte, error) {
  	var buildbotFormat *float64
  	if !t.Time.IsZero() {
  		usec := t.Time.Nanosecond() / 1e3
  		// avoid dividing big floating numbers
  		v := float64(t.Time.Unix()) + float64(usec)/1e6
  		buildbotFormat = &v
  	}
  	return json.Marshal(&buildbotFormat)
  }
docs: // MarshalJSON marshals t to JSON at microsecond resolution.