code: func sendCallbackID(callbacks map[string]dnode.Path, ch chan<- uint64) {
  	// TODO fix finding of responseCallback in dnode message when removing callback
  	for id, path := range callbacks {
  		if len(path) != 2 {
  			continue
  		}
  		p0, ok := path[0].(string)
  		if !ok {
  			continue
  		}
  		p1, ok := path[1].(string)
  		if !ok {
  			continue
  		}
  		if p0 != "0" || p1 != "responseCallback" {
  			continue
  		}
  		i, _ := strconv.ParseUint(id, 10, 64)
  		ch <- i
  		return
  	}
  	close(ch)
  }
docs: // sendCallbackID send the callback number to be deleted after response is received.