step2.go

func main() {
    port := 8080
    addr := fmt.Sprintf(":%d", port)
    mux := http.NewServeMux()
    mux.HandleFunc("/", indexHandler)
    mux.HandleFunc("/home", homeHandler)
    mux.HandleFunc("/async", serviceHandler)
    mux.HandleFunc("/service", serviceHandler)
    mux.HandleFunc("/db", dbHandler)
    fmt.Printf("Go to http://localhost:%d/home to start a request!\n", port)
    log.Fatal(http.ListenAndServe(addr, mux))
}