code: func (hub *hub) getChannel(name string) *channel {
  	hub.Lock()
  	defer hub.Unlock()
  	cn, ok := hub.channels[name]
  	if ok {
  		return cn
  	}
  	cn = makeChannel(hub, name)
  	hub.channels[name] = cn
  	go cn.start()
  	return cn
  }
docs: // GetChannel gets or creates new pubsub channel.