how to create pure++ http server (with own router and logging) - in less than 20 code lines [golang] [20lines]

main.go

package main

import (
	"log"
	"net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("ok"))
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", handler)

	if err := http.ListenAndServe(":8765", mux); err != nil {
		log.Fatalf("error at starting server: %s", err.Error())
	}
}