example: remove -qlog flag in favor of QLOGDIR (#4243)

example/client/main.go

@@ -1,13 +1,10 @@
 package main
 
 import (
-	"bufio"
 	"bytes"
-	"context"
 	"crypto/tls"
 	"crypto/x509"
 	"flag"
-	"fmt"
 	"io"
 	"log"
 	"net/http"
@@ -17,8 +14,6 @@ import (
 	"github.com/quic-go/quic-go"
 	"github.com/quic-go/quic-go/http3"
 	"github.com/quic-go/quic-go/internal/testdata"
-	"github.com/quic-go/quic-go/internal/utils"
-	"github.com/quic-go/quic-go/logging"
 	"github.com/quic-go/quic-go/qlog"
 )
 
@@ -26,7 +21,6 @@ func main() {
 	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")
-	enableQlog := flag.Bool("qlog", false, "output a qlog (in the same directory)")
 	flag.Parse()
 	urls := flag.Args()
 
@@ -46,25 +40,15 @@ func main() {
 	}
 	testdata.AddRootCA(pool)
 
-	var qconf quic.Config
-	if *enableQlog {
-		qconf.Tracer = func(ctx context.Context, p logging.Perspective, connID quic.ConnectionID) *logging.ConnectionTracer {
-			filename := fmt.Sprintf("client_%s.qlog", connID)
-			f, err := os.Create(filename)
-			if err != nil {
-				log.Fatal(err)
-			}
-			log.Printf("Creating qlog file %s.\n", filename)
-			return qlog.NewConnectionTracer(utils.NewBufferedWriteCloser(bufio.NewWriter(f), f), p, connID)
-		}
-	}
 	roundTripper := &http3.RoundTripper{
 		TLSClientConfig: &tls.Config{
 			RootCAs:            pool,
 			InsecureSkipVerify: *insecure,
 			KeyLogWriter:       keyLog,
 		},
-		QuicConfig: &qconf,
+		QuicConfig: &quic.Config{
+			Tracer: qlog.DefaultTracer,
+		},
 	}
 	defer roundTripper.Close()
 	hclient := &http.Client{