Now that we’ve made it through the Handler interface, let’s look at the first of the implementations provided by the standard library: the DiscardHandler.

var DiscardHandler Handler = discardHandler{}

DiscardHandler discards all log output. DiscardHandler.Enabled returns false for all Levels.

Why would you ever want a discard handler?

Two likely scenarios come to mind.

The one where I most frequently use it, is testing. You may not wish to log anything during a test, and this is a simple way to do that:

func TestFoo(t *testing.T) {
  logger := slog.New(slog.DiscardHandler)
  got, err := Foo(t.Context(), logger)
  if err != nil {
    t.Fatal(err)
  }
  if want := 42; got != want {
    t.Errorf("Foo returned an unexpected value: %v", got)
  }
}

The other use case would be a simple way to disable logging based on configuration or runtime state.

func initLogger() *slog.Logger {
  var handler slog.Handler
  if os.Getenv("DISABLE_LOGGING") != "" {
    handler = slog.DiscardHandler
  } else {
    handler = slog.NewJSONHandler(os.Stderr, nil)
  }
  return slog.New(handler)
}