helper.go
func WebSocketHandlerFunc(f func(ws *websocket.Conn)) HandlerFunc {
	h := websocket.Handler(f)
	return WrapHTTPHandlerFunc(h.ServeHTTP)
}
func WebSocketHandlerFunc(f func(ws *websocket.Conn)) HandlerFunc {
	h := websocket.Handler(f)
	return WrapHTTPHandlerFunc(h.ServeHTTP)
}
// WebSocketHandlerFunc convert websocket function to possum.HandlerFunc.