Package slogflags provides flags to configure log/slog.

Basic usage ¶

Simply call flag.Parse and then call Logger to obtain a configured slog instance. Two new flags will be available to users of your app: `--log.level` which accepts a textual level ("debug", "info", "warn" or "error") and `--log.format` which accepts either "text" or "json".

flag.Parse()
logger := slogflags.Logger()
logger.Warn("This is not a drill", "key", "value", "etc", "etc)

Custom levels ¶

If you define your own log levels, you can pass them to Logger using WithCustomLevels. Users can then specify them in the `log.level` flag.

Setting as the default logger ¶

Pass WithSetDefault(true) when calling Logger to register the new instance as the default logger for log/slog. You can then call log/slog.Warn etc directly.

Redirecting old log calls ¶

If your code or libraries use log rather than log/slog you can redirect them by setting a default logger as above. All log calls will be given the same log level, which you can alter using WithOldLogLevel. e.g.:

flag.Parse()
_ = slogflags.Logger(slogflags.WithSetDefault(true), slogflags.WithOldLogLevel(slog.LevelWarn))
log.Printf("hi")
// Prints: time=... level=WARN msg=hi

Other advanced usage ¶

You can customise other behaviour of the created logger using WithDefaultLogLevel, WithWriter, WithAddSource and WithReplaceAttr. See the documentation for those funcs for more details.

• func Logger(opts ...Option) *slog.Logger
• type Option
• • func WithAddSource(addSource bool) Option
  • func WithCustomLevels(levels map[string]slog.Level) Option
  • func WithDefaultLogLevel(level slog.Level) Option
  • func WithOldLogLevel(level slog.Level) Option
  • func WithReplaceAttr(fn func(groups []string, a slog.Attr) slog.Attr) Option
  • func WithSetDefault(setDefault bool) Option
  • func WithWriter(w io.Writer) Option

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