Understanding http request routing with net/http and gorilla/mux.

main.go

package main

import (
	"fmt"
	"net/http"
	"github.com/gorilla/mux"
)

func handler(name string)func (http.ResponseWriter, *http.Request) {
	dummyHandler := func (w http.ResponseWriter, r *http.Request) {
		route := mux.CurrentRoute(r)
		url := r.URL.String()
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.WriteHeader(http.StatusOK)
		fmt.Fprintf(w, "%s [%s] %s\n", route.GetName(), name, url)
		vars := mux.Vars(r)
		for k, v := range vars {
			fmt.Fprintf(w, "  [%s]: \"%s\"\n", k, v)
		}
	}
	return dummyHandler
}

func subsetup1(router *mux.Router, prefix string) {
	sub := router.PathPrefix(prefix).Subrouter()
	// there is no way to make 1.1 work - mux requires all patterns to start with '/'
	// sub.HandleFunc("", handler("router.subrouter")).Name("1.1")

	sub.HandleFunc("/", handler("router.subrouter/")).Name("1.2")
	sub.HandleFunc("/foo", handler("router.subrouter/foo")).Name("1.3")
	sub.HandleFunc("/foo/{id}", handler("router.subrouter/foo/id")).Name("1.4")

	// 1.1 workaround
	router.HandleFunc(prefix, handler("router.handlefunc")).Name("1.1")
}

func subsetup2(router *mux.Router, prefix string) {
	sub := mux.NewRouter()
	sub.HandleFunc(prefix, handler("router.handle")).Name("2.1")
	sub.HandleFunc(prefix + "/", handler("router.handle/")).Name("2.2")
	sub.HandleFunc(prefix + "/foo", handler("router.handle/foo")).Name("2.3")
	sub.HandleFunc(prefix + "/foo/{id}", handler("router.handle/foo/id")).Name("2.4")
	// required for 2.1
	router.Handle(prefix, sub)
	// required for 2.2 and 2.3
	router.Handle(prefix + "/{path:.*}", sub)
}

func subsetup3(router *mux.Router, prefix string) {
	sub := mux.NewRouter()
	sub.HandleFunc(prefix, handler("http.handle")).Name("3.1")
	sub.HandleFunc(prefix + "/", handler("http.handle/")).Name("3.2")
	sub.HandleFunc(prefix + "/foo", handler("http.handle/foo")).Name("3.3")
	sub.HandleFunc(prefix + "/foo/{id}", handler("http.handle/foo/id")).Name("3.4")
	// required for 3.1 (otherwise, 3.1 does not get called and net/http redirects you to 3.2)
	http.Handle(prefix, sub)
	// required for 3.2 and 3.3
	http.Handle(prefix + "/", sub)
}

func main() {
	router := mux.NewRouter()
	router.HandleFunc("/", handler("root/")).Name("0.1")

	subsetup1(router, "/s1")
	subsetup2(router, "/s2")
	subsetup3(router, "/s3")

	http.Handle("/", router)

	err := http.ListenAndServe(":1337", nil)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
	}
}

output

> curl http://127.0.0.1:1337
0.1 [root/] /

> curl http://127.0.0.1:1337/
0.1 [root/] /

> curl http://127.0.0.1:1337/s1
1.1 [router.handlefunc] /s1

> curl http://127.0.0.1:1337/s1/
1.2 [router.subrouter/] /s1/

> curl http://127.0.0.1:1337/s1/foo
1.3 [router.subrouter/foo] /s1/foo

> curl http://127.0.0.1:1337/s1/foo/1
1.4 [router.subrouter/foo/id] /s1/foo/1
  [id]: "1"

> curl http://127.0.0.1:1337/s2
2.1 [router.handle] /s2

> curl http://127.0.0.1:1337/s2/
2.2 [router.handle/] /s2/

> curl http://127.0.0.1:1337/s2/foo
2.3 [router.handle/foo] /s2/foo

> curl http://127.0.0.1:1337/s2/foo/2
2.4 [router.handle/foo/id] /s2/foo/2
  [id]: "2"

> curl http://127.0.0.1:1337/s3
3.1 [http.handle] /s3

> curl http://127.0.0.1:1337/s3/
3.2 [http.handle/] /s3/

> curl http://127.0.0.1:1337/s3/foo
3.3 [http.handle/foo] /s3/foo

> curl http://127.0.0.1:1337/s3/foo/3
3.4 [http.handle/foo/id] /s3/foo/3
  [id]: "3"