code: func NewWorker(c *Client, m WorkMap) *Worker {
  	return &Worker{
  		Interval: defaultWakeInterval,
  		Queue:    os.Getenv("QUE_QUEUE"),
  		c:        c,
  		m:        m,
  		ch:       make(chan struct{}),
  	}
  }
docs: // NewWorker returns a Worker that fetches Jobs from the Client and executes
  // them using WorkMap. If the type of Job is not registered in the WorkMap, it's
  // considered an error and the job is re-enqueued with a backoff.
  //
  // Workers default to an Interval of 5 seconds, which can be overridden by
  // setting the environment variable QUE_WAKE_INTERVAL. The default Queue is the
  // nameless queue "", which can be overridden by setting QUE_QUEUE. Either of
  // these settings can be changed on the returned Worker before it is started
  // with Work().