[SOLVED] Get a list of routes and params in Golang HTTP or Gorilla package

Get a list of routes and params in Golang HTTP or Gorilla package

When I write a simple web application like this:

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}

func main() {
    http.HandleFunc("/about", handler)
    http.ListenAndServe(":8080", nil)
}

How can I find the list of routes and params which I defined in my web app? e.g find "/about" in this example.

EDIT 1: How can get this one params and route?

gorilla.HandleFunc(`/check/{id:[0-9]+}`, func(res http.ResponseWriter, req *http.Request) {
    res.Write([]byte("Regexp works :)"))
})

Solution

With Go 1.22, or when using GO 1.21 with GODEBUG=httpmuxgo121=1:

You could use http.DefaultServeMux (type ServeMux) and examine it. With reflect package you can ValueOf the default multiplexer and extract m attribute which is a map of your routes.

v := reflect.ValueOf(http.DefaultServeMux).Elem()
fmt.Printf("routes: %v\n", v.FieldByName("mux121").FieldByName("m"))

With Go 1.21 or below:

You could use http.DefaultServeMux (type ServeMux) and examine it. With reflect package you can ValueOf the default multiplexer and extract m attribute which is a map of your routes.

v := reflect.ValueOf(http.DefaultServeMux).Elem()
fmt.Printf("routes: %v\n", v.FieldByName("m"))

upd:

if you use net/http than you should implement extracting params before any request is actually done by yourself; otherwise you have access to params with r.URL.Query()

if you use gorilla/mux than as elithrar mentioned you should use Walk:

func main:

r := mux.NewRouter()
r.HandleFunc("/path/{param1}", handler)

err := r.Walk(gorillaWalkFn)
if err != nil {
    log.Fatal(err)
}

func gorillaWalkFn:

func gorillaWalkFn(route *mux.Route, router *mux.Router, ancestors []*mux.Route) error {
    path, err := route.GetPathTemplate()
    return nil
}

the path variable contains your template:

"/path/{param1}"

but you should extract params manually.