event_bus.go
func New() Bus {
	b := &EventBus{
		make(map[string][]*eventHandler),
		sync.Mutex{},
		sync.WaitGroup{},
	}
	return Bus(b)
}
func New() Bus {
	b := &EventBus{
		make(map[string][]*eventHandler),
		sync.Mutex{},
		sync.WaitGroup{},
	}
	return Bus(b)
}
// New returns new EventBus with empty handlers.