cmd/go: silence TLS handshake errors during test

We don't need to see messages like "TLS handshake error: EOF"
during go test.

Change-Id: If6bf51e655119914f337b9e61448c99485af34f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/718183
Reviewed-by: Michael Matloob <matloob@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>

Author: rsc

src/cmd/go/internal/vcweb/vcstest/vcstest.go

@@ -7,6 +7,7 @@
 package vcstest
 
 import (
+	"bytes"
 	"cmd/go/internal/vcs"
 	"cmd/go/internal/vcweb"
 	"cmd/go/internal/web/intercept"
@@ -70,7 +71,9 @@ func NewServer() (srv *Server, err error) {
 		}
 	}()
 
-	srvHTTP := httptest.NewServer(handler)
+	srvHTTP := httptest.NewUnstartedServer(handler)
+	srvHTTP.Config.ErrorLog = testLogger()
+	srvHTTP.Start()
 	httpURL, err := url.Parse(srvHTTP.URL)
 	if err != nil {
 		return nil, err
@@ -81,7 +84,9 @@ func NewServer() (srv *Server, err error) {
 		}
 	}()
 
-	srvHTTPS := httptest.NewTLSServer(handler)
+	srvHTTPS := httptest.NewUnstartedServer(handler)
+	srvHTTPS.Config.ErrorLog = testLogger()
+	srvHTTPS.StartTLS()
 	httpsURL, err := url.Parse(srvHTTPS.URL)
 	if err != nil {
 		return nil, err
@@ -115,6 +120,19 @@ func NewServer() (srv *Server, err error) {
 	return srv, nil
 }
 
+func testLogger() *log.Logger {
+	return log.New(httpLogger{}, "vcweb: ", 0)
+}
+
+type httpLogger struct{}
+
+func (httpLogger) Write(b []byte) (int, error) {
+	if bytes.Contains(b, []byte("TLS handshake error")) {
+		return len(b), nil
+	}
+	return os.Stdout.Write(b)
+}
+
 func (srv *Server) Close() error {
 	if vcs.VCSTestRepoURL != srv.HTTP.URL {
 		panic("vcs URL hooks modified before Close")