code: func (m *Broadcaster) closeAll() {
  	m.lock.Lock()
  	defer m.lock.Unlock()
  	for _, w := range m.watchers {
  		close(w.result)
  	}
  	// Delete everything from the map, since presence/absence in the map is used
  	// by stopWatching to avoid double-closing the channel.
  	m.watchers = map[int64]*broadcasterWatcher{}
  }
docs: // closeAll disconnects all watchers (presumably in response to a Shutdown call).