to reproduce https://github.com/lucas-clemente/quic-go/issues/2551

main.go

package main

import (
	"crypto/tls"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"

	"github.com/lucas-clemente/quic-go"
	"github.com/lucas-clemente/quic-go/http3"
)

func main() {
	useQUIC := flag.Bool("quic", false, "use QUIC")
	flag.Parse()
	url := flag.Arg(0)
	if flag.NArg() < 1 {
		flag.Usage()
		os.Exit(1)
	}
	if err := run(url, *useQUIC); err != nil {
		log.Fatal(err)
	}
}

func run(url string, useQUIC bool) error {
	cl := http.Client{}
	if useQUIC {
		cl.Transport = &http3.RoundTripper{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
			QuicConfig: &quic.Config{
				GetLogWriter: func(connID []byte) io.WriteCloser {
					filename := fmt.Sprintf("%x.qlog", connID)
					f, err := os.Create(filename)
					if err != nil {
						log.Fatal(err)
					}
					fmt.Println("Created", filename)
					return f
				},
			},
		}
	} else {
		cl.Transport = &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		}
	}
	resp, err := cl.PostForm(url, map[string][]string{
		"foo": []string{"bar"},
		"key": []string{"val1", "val2"},
	})
	if err != nil {
		return err
	}
	fmt.Printf("Received response: %#v\n", resp)
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	fmt.Println("Body:", string(body))
	return nil
}