code: func (j *Job) Done() {
  	j.mu.Lock()
  	defer j.mu.Unlock()
  
  	if j.conn == nil || j.pool == nil {
  		// already marked as done
  		return
  	}
  
  	var ok bool
  	// Swallow this error because we don't want an unlock failure to cause work to
  	// stop.
  	_ = j.conn.QueryRow("que_unlock_job", j.ID).Scan(&ok)
  
  	j.pool.Release(j.conn)
  	j.pool = nil
  	j.conn = nil
  }
docs: // Done releases the Postgres advisory lock on the job and returns the database
  // connection to the pool.