http server replying with random data of requested size

main.go

// TODO describe program
package main

import (
	"fmt"
	"io"
	"math/rand"
	"net/http"
	"os"
	"strconv"
	"time"

	"github.com/artyom/autoflags"
)

func main() {
	args := &struct {
		Addr string `flag:"addr,address to listen"`
	}{Addr: "localhost:8080"}
	autoflags.Parse(args)
	if err := run(args.Addr); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}

func run(addr string) error {
	srv := &http.Server{
		Addr:              addr,
		Handler:           http.HandlerFunc(handleFunc),
		ReadHeaderTimeout: time.Second,
	}
	return srv.ListenAndServe()
}

func handleFunc(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		w.Header().Set("Accept", "GET")
		http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed)
		return
	}
	size, err := strconv.Atoi(r.URL.Query().Get("size"))
	if err != nil || size <= 0 {
		http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
		return
	}
	w.Header().Set("Content-Length", strconv.Itoa(size))
	w.Header().Set("Content-Type", "application/octet-stream")
	w.Header().Set("Content-Disposition", "attachment; filename=random.bin")
	io.Copy(w, io.LimitReader(rand.New(rand.NewSource(time.Now().Unix())), int64(size)))
}