code: func (as AtomicWebSocketSet) NotifySockets(uid uint64, cmd, ret string) error {
  	s := as.Get(uid)
  	if s == nil {
  		// Trainer is not online.
  		return nil
  	}
  	t := time.Now()
  	data := []struct {
  		Sentence  string
  		AvaSent   bool
  		CreatedAt *time.Time
  	}{
  		{
  			Sentence:  cmd,
  			AvaSent:   false,
  			CreatedAt: &t,
  		},
  	}
  	if len(ret) > 0 {
  		data = append(data, struct {
  			Sentence  string
  			AvaSent   bool
  			CreatedAt *time.Time
  		}{
  			Sentence:  ret,
  			AvaSent:   true,
  			CreatedAt: &t,
  		})
  	}
  	return websocket.JSON.Send(s, &data)
  }
docs: // NotifySockets sends listening clients new messages over WebSockets,
  // eliminating the need for trainers to constantly reload the page.