code: func (callflow CallFlow) MarshalJSON() ([]byte, error) {
  	data := jsonCallFlow{
  		ID:    callflow.ID,
  		Title: callflow.Title,
  		// Steps are able to serialize themselves to JSON.
  		Steps:     callflow.Steps,
  		Record:    callflow.Record,
  		CreatedAt: callflow.CreatedAt.Format(time.RFC3339),
  		UpdatedAt: callflow.UpdatedAt.Format(time.RFC3339),
  	}
  	return json.Marshal(data)
  }
docs: // MarshalJSON implements the json.Marshaler interface.