chain.go
func FinalHandlerFunc(h func(w http.ResponseWriter, r *http.Request)) func(http.Handler) http.Handler {
	return func(_ http.Handler) http.Handler {
		return http.HandlerFunc(h)
	}
}
func FinalHandlerFunc(h func(w http.ResponseWriter, r *http.Request)) func(http.Handler) http.Handler {
	return func(_ http.Handler) http.Handler {
		return http.HandlerFunc(h)
	}
}
// FinalHandlerFunc is a helper function to wrap the last function with signature
// func(w http.ResponseWriter, r *http.Request) in the ChainHandlers function.