A demo of the different ways to hit http.ServeMux (standard library router) when making a webserver in Go

main.go

// Context: https://rickyanto.com/understanding-go-standard-http-libraries-servemux-handler-handle-and-handlefunc/
package main

import (
	"fmt"
	"net/http"
)

func handlerFunc(w http.ResponseWriter, r *http.Request) {
	// w.Header().Set("Content-Type", "text/html")
	fmt.Fprintf(w, "Hello World!")
}

type Sample struct{}

func (s *Sample) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, "Hello World")
}

// A sample implementation to demonstrate the different ways
// to route using the net/http package.
//
// Version 1:
// Simplest method, define a 'HandlerFunc' interface and pass it
// to the http.HandleFunc method. Internally, http instantiates
// its own default ServeMux and passes the args on that that
// ServeMux object's 'HandleFunc' method
//
// Version 2:
// Define a struct that implements the HandleFunc interface in a
// 'ServeHTTP' method. Pass a pointer to the an instance of the
// struct to http.Handle. http passes it on to its internal default
// ServeMux.Handle method.
//
// Version 3:
// Same as Version 1 except we explictly instantiate an http.ServeMux,
// call the HandleFunc methodon that instance instead, and then pass
// that instance into http.ListenAndServe.
//
// Version 4:
// Same as Version 2 except we explictly instantiate an http.ServeMux,
// call the Handle method on that instance instead, and then pass that
// instance into http.ListenAndServe.
//
// Uncomment according to the 'Version' comments below to see the
// different options in action.
func serveDemo() {
	// Handle-compatible interface
	// t := Sample{} // Version 2, Version 4

	// http default ServeMux
	http.HandleFunc("/", handlerFunc) // Version 1
	// http.Handle("/", &t) // Version 2

	// Explicit ServeMux instance
	// r := http.NewServeMux() // Version 3, Version 4
	// r.HandleFunc("/", handlerFunc) // Version 3
	// r.Handle("/", &t) // Version 4

	fmt.Println("Server started at localhost:3000")
	http.ListenAndServe(":3000", nil) // Version 1, Version 2
	// http.ListenAndServe(":3000", r) // Version 3, Version 4
}

func main() {
	serveDemo()
}