code: func readTaskData(ctl task.Controller) (*taskData, error) {
  	td := &taskData{}
  	if err := json.Unmarshal(ctl.State().TaskData, td); err != nil {
  		return nil, errors.Annotate(err, "could not parse TaskData").Err()
  	}
  	return td, nil
  }
docs: // readTaskData parses task data blob as prepared by writeTaskData.