code: func (j *Job) Duration() time.Duration {
  	if j.Finished().IsZero() {
  		return 0 * time.Second
  	}
  	return j.Finished().Sub(j.Started())
  }
docs: // Duration returns how long the job took to execute with nanosecond
  // precision. I.e. the difference between j.Finished() and j.Started().
  // It returns a duration of zero if the job has not finished yet.