Send JSON encoded payloads without re-marshalling them?

[grandstairs]

I would like to use this library as the basis for multiple logging libraries. However, the only way I was able to figure was to create an io.WriteCloser that wraps this library to do the .Post(tag, data) with the actual log line.

type FluentWriter struct {
	Fluent *fluent.Fluent
	Tag    string
}

func (w *FluentWriter) Close() error {
	return w.Fluent.Close()
}

func (f *FluentWriter) Write(p []byte) (n int, err error) {
	// this is wasteful since the logger just spent time to json.Encode this very payload.
	msg := map[string]interface{}{}
	json.Unmarshal(p, &msg)
	err = f.Fluent.Post(f.Tag, msg)
	return len(p), err
}

The issue is that Post() and EncodeAndPostData() both expect an non-encoded map/struct/interface which isn't the b []byte that an io.Writer provides.

f, err := fluent.New(fluent.Config{});
logSink := &logger.FluentWriter{Fluent: f, Tag: "ApplicationLogs"}
logger := zerolog.New(logSink).With().Timestamp().Logger()

Is there either 1) a better way to wrap this library so I can avoid this encode/decode/encode process or 2) is there a way to send a raw b []byte payload via msgpack without fluent-logger-golang needing to mess with it?

As-is, there really isn't much performance savings going with zerolog or zap over using something like slog or logrus because there will be a ton of extra memory allocations running the JSON encoder/decoder over the payloads.