Close the log Writer used for the std log

cmd/root.go

@@ -242,7 +242,18 @@ func (c *rootCommand) persistentPreRunE(cmd *cobra.Command, args []string) error
 		c.loggerIsRemote = true
 	}
 
-	stdlog.SetOutput(c.globalState.logger.Writer())
+	// Sometimes the Go runtime uses the standard log output to
+	// log some messages directly.
+	// It does when an invalid char is found in a Cookie.
+	// Check for details https://github.com/grafana/k6/issues/711#issue-341414887
+	stdlog.SetOutput(func() io.Writer {
+		w := c.globalState.logger.Writer()
+		go func() {
+			<-c.globalState.ctx.Done()
+			_ = w.Close()
+		}()
+		return w
+	}())
 	c.globalState.logger.Debugf("k6 version: v%s", consts.FullVersion())
 	return nil
 }

cmd/root_test.go

@@ -61,10 +61,7 @@ func TestMain(m *testing.M) {
 	}()
 
 	defer func() {
-		// TODO: figure out why logrus' `Entry.WriterLevel` goroutine sticks
-		// around and remove this exception.
-		opt := goleak.IgnoreTopFunction("io.(*pipe).read")
-		if err := goleak.Find(opt); err != nil {
+		if err := goleak.Find(); err != nil {
 			fmt.Println(err) //nolint:forbidigo
 			exitCode = 3
 		}
@@ -91,6 +88,10 @@ func getFreeBindAddr(t *testing.T) string {
 	for i := 0; i < 100; i++ {
 		port := atomic.AddUint64(&portRangeStart, 1)
 		addr := net.JoinHostPort("localhost", strconv.FormatUint(port, 10))
+        :q
+        :q
+        :q
+        :q
 
 		listener, err := net.Listen("tcp", addr)
 		if err != nil {

cmd/stdlog_integration_test.go

@@ -0,0 +1,48 @@
+package cmd
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.k6.io/k6/lib/testutils/httpmultibin"
+)
+
+// SetOutput sets the global log so it is racy with other tests
+//
+//nolint:paralleltest
+func TestStdLogOutputIsSet(t *testing.T) {
+	tb := httpmultibin.NewHTTPMultiBin(t)
+	ts := newGlobalTestState(t)
+
+	// Sometimes the Go runtime uses the standard log output to
+	// log some messages directly.
+	// It does when an invalid char is found in a Cookie.
+	// Check for details https://github.com/grafana/k6/issues/711#issue-341414887
+	ts.stdIn = bytes.NewReader([]byte(tb.Replacer.Replace(`
+import http from 'k6/http';
+
+ export const options = {
+      hosts: {
+        "HTTPSBIN_DOMAIN": "HTTPSBIN_IP",
+      },
+      insecureSkipTLSVerify: true,
+    }
+
+export default function () {
+      http.get("HTTPSBIN_URL/get", {
+		"cookies": {
+			"test": "\""
+		},
+	})
+}`)))
+
+	ts.args = []string{"k6", "version"}
+	ts.args = []string{"k6", "run", "-i", "1", "-"}
+	newRootCommand(ts.globalState).execute()
+
+	entries := ts.loggerHook.Drain()
+	require.Len(t, entries, 1)
+	assert.Contains(t, entries[0].Message, "Cookie.Value; dropping invalid bytes")
+}