event

type Bus interface {
	BusSubscriber
	BusPublisher
}

type BusPublisher interface {
	Publish(topic string, args ...interface{})
}

type BusSubscriber interface {
	Subscribe(topic string, fn interface{}) error
	SubscribeAsync(topic string, fn interface{}, transactional bool) error
	Unsubscribe(topic string, handler interface{}) error
}

type EventContext struct {
	context.Context
	Publisher interface{}
	Param     interface{}
}

type EventHandler func(ctx EventContext)

type Subscriber struct {
	Topic string
	Fn    EventHandler
}