src/log/slog/example_logvaluer_secret_test.go

// Copyright 2022 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 (
	"log/slog"
	"os"
)

// A token is a secret value that grants permissions.
type Token string

// LogValue implements slog.LogValuer.
// It avoids revealing the token.
func (Token) LogValue() slog.Value {
	return slog.StringValue("REDACTED_TOKEN")
}

// This example demonstrates a Value that replaces itself
// with an alternative representation to avoid revealing secrets.
func ExampleLogValuer_secret() {
	t := Token("shhhh!")
	removeTime := func(groups []string, a slog.Attr) slog.Attr {
		if a.Key == slog.TimeKey && len(groups) == 0 {
			return slog.Attr{}
		}
		return a
	}
	logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ReplaceAttr: removeTime}))
	logger.Info("permission granted", "user", "Perry", "token", t)

	// Output:
	// level=INFO msg="permission granted" user=Perry token=REDACTED_TOKEN
}