code: func (c *cache) notify(id types.UID, timestamp time.Time) {
  	list, ok := c.subscribers[id]
  	if !ok {
  		// No one to notify.
  		return
  	}
  	newList := []*subRecord{}
  	for i, r := range list {
  		if timestamp.Before(r.time) {
  			// Doesn't meet the time requirement; keep the record.
  			newList = append(newList, list[i])
  			continue
  		}
  		r.ch <- c.get(id)
  		close(r.ch)
  	}
  	if len(newList) == 0 {
  		delete(c.subscribers, id)
  	} else {
  		c.subscribers[id] = newList
  	}
  }
docs: // notify sends notifications for pod with the given id, if the requirements
  // are met. Note that the caller should acquire the lock.