client.go
func (client *Client) Subscribe(topic string, fn interface{}, serverAddr, serverPath string) {
	client.doSubscribe(topic, fn, serverAddr, serverPath, Subscribe)
}
func (client *Client) Subscribe(topic string, fn interface{}, serverAddr, serverPath string) {
	client.doSubscribe(topic, fn, serverAddr, serverPath, Subscribe)
}
//Subscribe subscribes to a topic in a remote event bus