pubsub.go
func WithValidatorConcurrency(n int) ValidatorOpt {
	return func(addVal *addValReq) error {
		addVal.throttle = n
		return nil
	}
}
func WithValidatorConcurrency(n int) ValidatorOpt {
	return func(addVal *addValReq) error {
		addVal.throttle = n
		return nil
	}
}
// WithValidatorConcurrency is an option that sets topic validator throttle.