single    [handlerLast]SingleHandlerFn
	stateless [handlerLast]*StatelessHandler
	streams   [handlerLast]*StreamHandler

	subSingle    map[subHandlerID]SingleHandlerFn
	subStateless map[subHandlerID]*StatelessHandler
	subStreams   map[subHandlerID]*StreamHandler
}

func (h *handlers) init() {
	h.subSingle = make(map[subHandlerID]SingleHandlerFn)
	h.subStateless = make(map[subHandlerID]*StatelessHandler)