Gorilla mux routing by queries example.

example.go

package main

import (
	"fmt"
	"net/http"

	"github.com/gorilla/mux"
)

type itemHandler struct {
	router *mux.Router
}

func (h *itemHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	item := vars["item"]
	version := vars["version"]
	route := h.getRoute(version)
	u, err := route.URL("item", item, "version", version)
	if err != nil {
		panic(fmt.Sprintf("Failed to make URL with route: %v", err))
	}

	fmt.Fprintf(w, "Item: %q\n", item)
	fmt.Fprintf(w, "Version: %q\n", version)
	fmt.Fprintf(w, "Reversed URL: %q\n", u.String())
}

func (h *itemHandler) getRoute(version string) *mux.Route {
	name := h.getRouteName(version)
	route := h.router.GetRoute(name)
	if route == nil {
		panic(fmt.Sprintf("Cannot find route %q", name))
	}
	return route
}

func (h *itemHandler) getRouteName(version string) string {
	if version == "" {
		return "item"
	}
	return "item/version"
}

func registerItemHandler(router *mux.Router) {
	router.Methods("GET").Handler(&itemHandler{router})
}

// Main function
func main() {
	router := mux.NewRouter().StrictSlash(true)
	itemsRouter := router.PathPrefix("/items/").Name("items").Subrouter().StrictSlash(true)
	itemRouter := itemsRouter.Path("/{item}").Name("item").Subrouter()
	registerItemHandler(itemRouter.Queries("version", "{version}").Name("item/version").Subrouter())
	registerItemHandler(itemRouter)

	err := http.ListenAndServe(":8080", router)
	if err != nil {
		fmt.Println(err)
	}
}