cleartext http2 server, code is from https://go.googlesource.com/net/+/master/http2/transport_test.go

h2c.go

package main

import (
	"log"
	"os"
	"net/http"
	"net"
	"crypto/tls"
	"golang.org/x/net/http2"
	"fmt"
)

func newLocalListener(addr string) net.Listener {
	l, err := net.Listen("tcp", addr)
	if err != nil {
		panic(err)
	}
	return l
}

type fakeTLSConn struct {
	net.Conn
}

func (c *fakeTLSConn) ConnectionState() tls.ConnectionState {
	return tls.ConnectionState{
		Version:     tls.VersionTLS12,
		CipherSuite: 0xC02F, // cipher_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
	}
}

func startH2cServer(addr string, handler http.Handler) net.Listener {
	h2Server := &http2.Server{MaxConcurrentStreams: 5000}
	l := newLocalListener(addr)
	defer l.Close()
	for {
		conn, err := l.Accept()
		if err != nil {
			log.Println("accepting error", err)
			continue
		}
		h2Server.ServeConn(&fakeTLSConn{conn}, &http2.ServeConnOpts{Handler: handler})
	}
}
func main() {
	if len(os.Args) != 2 {
		log.Printf("Usage %s :8080 \n", os.Args[0])
		return
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "url: %v, http: %v", r.URL.Path, r.TLS == nil)
	})

	startH2cServer(os.Args[1], mux)
}