code: func (h *handler) cancelServerSubscriptions(err error) {
  	h.subLock.Lock()
  	defer h.subLock.Unlock()
  
  	for id, s := range h.serverSubs {
  		s.err <- err
  		close(s.err)
  		delete(h.serverSubs, id)
  	}
  }
docs: // cancelServerSubscriptions removes all subscriptions and closes their error channels.