code: func (q *Queue) Events() EventMask {
  	ret := EventMask(0)
  
  	q.mu.RLock()
  	for e := q.list.Front(); e != nil; e = e.Next() {
  		ret |= e.mask
  	}
  	q.mu.RUnlock()
  
  	return ret
  }
docs: // Events returns the set of events being waited on. It is the union of the
  // masks of all registered entries.