go-httpmux-example

Simple exmaple to show how to use of new http.ServeMux router in Go v1.22.x.

Pre-requisite

• First, update your Go tools to version v1.22.0 or higher
• If you are planning to use the new enhance routing feaure in an existing Go module/project, make sure to change the Go version in your go.mod file to go 1.22.0 or whatever future version you are using (to avoid frustration trying to figure out why the feature is not working).

Enhanced Pattern Matching for Go 1.22 http.ServeMux

Go's standard library has long provided a powerful and efficient way to route web requests with the http package. Go 1.22 introduced a new pattern matching feature that makes HTTP request routing more flexible.

• As a convenience, you can embed allowed HTTP methods (e.g., "GET", "POST") directly in the route along with the path.
• Path patterns can wildcards with named variables denoted using curly braces.
• Mechanism to extract path variables from the URL and made available to the handler.

Benefits

• Combining the allowed HTTP method along with the path provides a clean, expressive, and RESTful routing patterns.
• Support for path variables reduces the logic necessary to extract values from the URL within your handler functions.

Example

The code is a simple demostration of the new feature:

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /tasks", getTasks)
	mux.HandleFunc("GET /tasks/{id}", getTask)
	mux.HandleFunc("POST /tasks/create", postTask)
	fmt.Println("Starting server on port 8080")
	http.ListenAndServe(":8080", mux)
}

Method call mux.HandleFunc("GET /tasks", getTasks) does two things:

• It specifies that the request will only work for a GET request.
• And will only work for request with paths that start with /tasks

As mentioned, the request pattern can include a request path variable: mux.HandleFunc("GET /tasks/{id}", getTask). In your handler, you can now use the new Request.PathValue method to extract the path variable.

For instance, curl http://localhost:8080/tasks/four would trigger the following handler:

func getTask(w http.ResponseWriter, r *http.Request) {
	idStr := r.PathValue("id")

	lock.RLock()
	task, ok := tasks[idStr]
	lock.RUnlock()

	if !ok {
		http.NotFound(w, r)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(task); err != nil {
		http.Error(w, "Error encountered", http.StatusInternalServerError)
	}
}

References

You can read more about the new http.ServeMux routing enhancements to get a better picture of its capabilities:

• Routing enhancements for Go v1.22.0 - Go blog
• net/http.ServMux source code documentation