hub.go
func (hub *hub) Publish(channels []string, msg interface{}) {
	for _, name := range channels {
		var cn = hub.getChannel(name)
		cn.Publish(msg)
	}
}
func (hub *hub) Publish(channels []string, msg interface{}) {
	for _, name := range channels {
		var cn = hub.getChannel(name)
		cn.Publish(msg)
	}
}
// Publish data to given channel.