helloworld.go

func main() {
	r := mux.NewRouter()

	r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {

		rand.Seed(time.Now().UnixNano())
		n := rand.Intn(10) // n will be between 0 and 10
		fmt.Printf("randon number was %d\n", n)
		if n < 6 {
			http.Error(w, "error!", 500)

		} else {
			fmt.Fprintf(w, "Hello World!")
		}

	})

	http.ListenAndServe(":8080", r)
}