code: func tryEnqueue(job PushNotification, jobChan chan<- PushNotification) bool {
  	select {
  	case jobChan <- job:
  		return true
  	default:
  		return false
  	}
  }
docs: // tryEnqueue tries to enqueue a job to the given job channel. Returns true if
  // the operation was successful, and false if enqueuing would not have been
  // possible without blocking. Job is not enqueued in the latter case.