golang httprouter disable access index folder but allow for dynamic filename to serve files

golang_httprouter_disable_access_dir.go

// import "github.com/julienschmidt/httprouter"
// example router
// Serve static files for Assets
router := httprouter.New()

router.GET("/fonts/*filepath", fileHandler("/fonts/"))
router.GET("/styles/*filepath", fileHandler("/styles/"))
router.GET("/scripts/*filepath", fileHandler("/scripts/"))
router.GET("/img/*filepath", fileHandler("/img/"))

// fileHandler to handle directory index
func fileHandler(folder string) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
		fileReq := p.ByName("filepath")
		// disable / or /assets/childdirective/../
		if fileReq == "/" || (len(fileReq) > 1 && fileReq[len(fileReq)-1:] == "/") {
			w.WriteHeader(http.StatusNotFound)
			fmt.Fprint(w, "404 page not found")
			return
		}

		r.URL.Path = fileReq
		fileServer := http.FileServer(http.Dir(fmt.Sprintf("%v%v", "/var/www", folder)))
		fileServer.ServeHTTP(w, r)
	}
}