code: func Open(URL ...string) (pubsub.Hub, error) {
  	redisURL := getRedisURL(URL...)
  	conn, err := redisurl.ConnectToURL(redisURL)
  	if err != nil {
  		return nil, err
  	}
  	return &hub{
  		conn:     conn,
  		redisURL: redisURL,
  		subs:     make(map[*sub]struct{}),
  	}, nil
  }
docs: // Open creates pubsub hub connected to redis server.