[BUG] Memory leaks caused by time.After

[biningo]

Describe the bug
timer.After() creates a new timer object each time it is called. Which can cause a memory leak in the for loop.

asynq/subscriber.go

Lines 61 to 74 in d04888e

	for {
	pubsub, err = s.broker.CancelationPubSub()
	if err != nil {
	s.logger.Errorf("cannot subscribe to cancelation channel: %v", err)
	select {
	case <-time.After(s.retryTimeout):
	continue
	case <-s.done:
	s.logger.Debug("Subscriber done")
	return
	}
	}
	break
	}

asynq/syncer.go

Lines 60 to 85 in d04888e

	for {
	select {
	case <-s.done:
	// Try sync one last time before shutting down.
	for _, req := range requests {
	if err := req.fn(); err != nil {
	s.logger.Error(req.errMsg)
	}
	}
	s.logger.Debug("Syncer done")
	return
	case req := <-s.requestsCh:
	requests = append(requests, req)
	case <-time.After(s.interval):
	var temp []*syncRequest
	for _, req := range requests {
	if req.deadline.Before(time.Now()) {
	continue // drop stale request
	}
	if err := req.fn(); err != nil {
	temp = append(temp, req)
	}
	}
	requests = temp
	}
	}

To Reproduce

Expected behavior
Creating the timer object before the for loop.

Screenshots

Environment (please complete the following information):

• OS: Linux
• Version of asynq package v0.24.1

Additional context