matevskial/nestedservemux

An example repo to reproduce a problem with nesting http serve mux in go

An example project to reproduce a problem with nesting http serve mux

Description

Suppose you have restful api like POST for /api/users and POST for /api/posts

And suppose we would like to implement these restful api's by nesting the httpServeMux like in the snipper below:

userHandler := userHandler{}
postHandler := postHandler{}

httpServeMux := http.NewServeMux()
httpServeMux.Handle("/api/users/", http.StripPrefix("/api/users", userHandler.Handler())
httpServeMux.Handle("/api/posts/", http.StripPrefix("/api/posts", postHandler.Handler()

where, for example, userHandler.Handler() implementation looks like:

func (u *userHandler) Handler() http.Handler {
    httpServeMux := http.NewServeMux()
    httpServeMux.HandleFunc("POST /", func(w http.ResponseWriter, req *http.Request) { /* should handle POST /api/users */ }
    return httpServeMux
}

The implementation of postHandler.Handler() is similar.

The problem with this implementation is that calling POST /api/users(NO trailing slash) result in 405 Method not Allowed.

Please note that it WORKS FINE when calling POST /api/users/(note the trailing slash)

Additionally, if we have an additional GET request handler, the userHandler.Handler() would then look like:

func (u *userHandler) Handler() http.Handler {
    httpServeMux := http.NewServeMux()
    httpServeMux.HandleFunc("GET /", func(w http.ResponseWriter, req *http.Request) { /* should handle GET /api/users */ }
    httpServeMux.HandleFunc("POST /", func(w http.ResponseWriter, req *http.Request) { /* should handle POST /api/users */ }
    return httpServeMux
}

then calling GET /api/users(NO trailing slash) and GET /api/users/(note the trailing slash) are working.

Calls to POST /api/users/(note the trailing slash) are working fine.

But calls POST /api/users(NO trailing slash) are actually handled by the GET handler, what's going on?

Is this a bug or an intended behavior?

Instructions to reproduce

1. Clone repo and navigate to the root of this repo.

2. Run the program by

go run .

3. Test with Postman(a collection with v2.1 format is included in the repo). For some reason, I am unable to test any of the endpoints with cURL because it always results with 301 Moved Permanently when testing without trailing slash. Still, here are the cURL requests:

curl http://localhost:8080/api/users

curl -X POST http://localhost:8080/api/users

4. These cURL command work same both with cURL and Postman.

curl http://localhost:8080/api/users/

curl -X POST http://localhost:8080/api/users/