code: func (hub *hub) Subscribe(channels []string) (Channel, error) {
  	var chans []*channel
  	for _, name := range channels {
  		chans = append(chans, hub.getChannel(name))
  	}
  	var sub = makeSub(chans)
  	for _, cn := range chans {
  		cn.Subscribe(sub)
  	}
  	return sub, nil
  }
docs: // Subscribe adds new receiver of events for given channel.