// StatelessHandler is handlers for one to many requests,
	// where responses may be dropped.
	// Stateless requests provide no incoming stream and there is no flow control
	// on outgoing messages.
	StatelessHandler struct {
		Handle StatelessHandlerFn
		// OutCapacity is the output capacity on the caller.
		// If <= 0 capacity will be 1.
		OutCapacity int
	}