eventbus

type EventBus interface {
	Subscribe(topic string, fn interface{}) error
	SubscribeAsync(topic string, fn interface{}, transactional bool) error
	SubscribeOnce(topic string, fn interface{}) error
	SubscribeOnceAsync(topic string, fn interface{}) error
	HasCallback(topic string) bool
	Unsubscribe(topic string, handler interface{}) error
	Publish(topic string, args ...interface{})
	WaitAsync()
}