code: func (el *ChannelEventListener) Close() error {
  	el.idsMu.Lock()
  	defer el.idsMu.Unlock()
  	for _, id := range el.ids {
  		if err := el.em.UnregisterListener(id); err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // Close frees up all underlying channels from the EventMachine.