From b412ed6d30bf03e13b446388fc2a55b80d28426f Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Tue, 11 Feb 2020 13:22:11 +0700
Subject: [PATCH] add a command line option to the example client to export a
 key log file

---
 example/client/main.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/example/client/main.go b/example/client/main.go
index 5935e23eb..8f2c6a3d1 100644
--- a/example/client/main.go
+++ b/example/client/main.go
@@ -8,6 +8,7 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"os"
 	"sync"
 
 	"github.com/lucas-clemente/quic-go/http3"
@@ -18,6 +19,7 @@ import (
 func main() {
 	verbose := flag.Bool("v", false, "verbose")
 	quiet := flag.Bool("q", false, "don't print the data")
+	keyLogFile := flag.String("keylog", "", "key log file")
 	insecure := flag.Bool("insecure", false, "skip certificate verification")
 	flag.Parse()
 	urls := flag.Args()
@@ -31,6 +33,16 @@ func main() {
 	}
 	logger.SetLogTimeFormat("")
 
+	var keyLog *os.File
+	if len(*keyLogFile) > 0 {
+		var err error
+		keyLog, err = os.Create(*keyLogFile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer keyLog.Close()
+	}
+
 	pool, err := x509.SystemCertPool()
 	if err != nil {
 		log.Fatal(err)
@@ -40,6 +52,7 @@ func main() {
 		TLSClientConfig: &tls.Config{
 			RootCAs:            pool,
 			InsecureSkipVerify: *insecure,
+			KeyLogWriter:       keyLog,
 		},
 	}
 	defer roundTripper.Close()