Create a "delayed" JavaScript file

slownet.go

// Usage: Send GET request to /<seconds> to wait <seconds> seconds
package main

import (
	"net/http"
	"strconv"
	"time"
)

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		delay, err := strconv.Atoi(r.URL.Path[1:])
		if err != nil {
			delay = 3
		}
		time.Sleep(time.Duration(delay) * time.Second)
		w.Header().Set("Content-type", "text/javascript")
		w.Write([]byte(`console.log("loaded!");`))
	})

	panic(http.ListenAndServe(":10101", nil))
}