Go: Wrap HTTP mux

main.go

package main

import (
	"fmt"
	"log"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
)

func main() {
	// People create their own thing, as they wish, with what ever lib.
	r := chi.NewRouter()
	r.Use(middleware.Logger)
	r.Get("/ping", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("pong"))
	})

	// And they pass it down to us so we "wrap" it.
	fmt.Println("Starting server on 8080")
	srv := NewHTTPServer(8080, r)
	if err := srv.ListenAndServe(); err != nil {
		log.Printf("server ended: %s", err.Error())
	}
}

func NewHTTPServer(port int, mux http.Handler) *http.Server {
	// Create a root mux where we will add all the stuff we want to, such as the
	// health endpoints.
	rootMux := http.NewServeMux()
	rootMux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(200)
	})

	// We apply all the middlewares we want to the provided router.
	rootMux.Handle("/", exampleMiddleware(mux))

	// Return the server.
	return &http.Server{Addr: fmt.Sprintf(":%d", port), Handler: rootMux}
}

func exampleMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Println("Running before handler")
		_, _ = w.Write([]byte("Hijacking Request "))
		next.ServeHTTP(w, r)
		fmt.Println("Running after handler")
	})
}