log/slog: add multiple handlers support for logger

Fixes #65954

Change-Id: Ib01c6f47126ce290108b20c07479c82ef17c427c
GitHub-Last-Rev: 34a36ea4bf099b2ad30f35e639155853ff73ef46
GitHub-Pull-Request: golang/go#74840
Reviewed-on: https://go-review.googlesource.com/c/go/+/692237
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/src/log/slog/example_multi_handler_test.go b/src/log/slog/example_multi_handler_test.go
new file mode 100644
index 0000000000..daba82c47d
--- /dev/null
+++ b/src/log/slog/example_multi_handler_test.go
@@ -0,0 +1,39 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package slog_test
+
+import (
+	"bytes"
+	"log/slog"
+	"os"
+)
+
+func ExampleMultiHandler() {
+	removeTime := func(groups []string, a slog.Attr) slog.Attr {
+		if a.Key == slog.TimeKey && len(groups) == 0 {
+			return slog.Attr{}
+		}
+		return a
+	}
+
+	var textBuf, jsonBuf bytes.Buffer
+	textHandler := slog.NewTextHandler(&textBuf, &slog.HandlerOptions{ReplaceAttr: removeTime})
+	jsonHandler := slog.NewJSONHandler(&jsonBuf, &slog.HandlerOptions{ReplaceAttr: removeTime})
+
+	multiHandler := slog.NewMultiHandler(textHandler, jsonHandler)
+	logger := slog.New(multiHandler)
+
+	logger.Info("login",
+		slog.String("name", "whoami"),
+		slog.Int("id", 42),
+	)
+
+	os.Stdout.WriteString(textBuf.String())
+	os.Stdout.WriteString(jsonBuf.String())
+
+	// Output:
+	// level=INFO msg=login name=whoami id=42
+	// {"level":"INFO","msg":"login","name":"whoami","id":42}
+}