golang use closure and wrap error

golang_closure_error.go

func listHandler(w http.ResponseWriter, r *http.Request) {
    fileInfoArr, err := ioutil.ReadDir("./uploads")         
    check(err)
    locals := make(map[string]interface{})
    images := []string{}
    for _, fileInfo := range fileInfoArr {
        images = append(images, fileInfo.Name)
    }
    locals["images"] = images
    renderHtml(w, "list", locals)
}

func safeHandler(fn http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        defer func() {
            if e, ok := recover().(error); ok {
                http.Error(w, err.Error(), 
                    http.StatusInternalServerError)                      
                // out put custom 50x error page
                // w.WriteHeader(http.StatusInternalServerError)
                // renderHtml(w, "error", e)                      
                // logging
                log.Println("WARN: panic in %v. - %v", fn, e)
                log.Println(string(debug.Stack()))
            }
        }()
        fn(w, r)
    }
}

func main() {
    mux := http.NewServeMux()
    staticDirHandler(mux, "/assets/", "./public", 0)
    //mux.HandleFunc("/", listHandler)
    mux.HandleFunc("/", safeHandler(listHandler))
    err := http.ListenAndServe(":8080", mux)
    if err != nil {
        log.Fatal("ListenAndServe: ", err.Error())
    }
}