func (n *NopPubSub) Publish(fromID, key string) error {
	return nil
}
Publish does nothing for NopPubSub
package eventbus
type PubSub interface {
	Publish(fromID, key string) error
	Subscribe(fn func(fromID, key string)) error
}
type NopPubSub struct{}
func (n *NopPubSub) Subscribe(fn func(fromID, key string)) error {
	return nil
}