slog handler that pulls request id from context and adds it to traces

requestIDHandler.go

package http

import (
	"context"
	"log/slog"
)

// RequestAttrGrabber adds an attribute to each row produced by the logger when it can
type RequestAttrGrabber struct {
	Sub         slog.Handler
	AttrGrabber func(ctx context.Context) string
	Key         string
}

func (r RequestAttrGrabber) Enabled(ctx context.Context, l slog.Level) bool {
	return r.Sub.Enabled(ctx, l)
}

func (r RequestAttrGrabber) Handle(ctx context.Context, rec slog.Record) error {
	if id := r.AttrGrabber(ctx); id != "" {
		rec.AddAttrs(slog.String(r.Key, id))
	}

	return r.Sub.Handle(ctx, rec)
}

func (r RequestAttrGrabber) WithAttrs(attrs []slog.Attr) slog.Handler {
	return RequestAttrGrabber{
		AttrGrabber: r.AttrGrabber,
		Key:         r.Key,
		Sub:         r.Sub.WithAttrs(attrs),
	}
}

func (r RequestAttrGrabber) WithGroup(name string) slog.Handler {
	return RequestAttrGrabber{
		AttrGrabber: r.AttrGrabber,
		Key:         r.Key,
		Sub:         r.Sub.WithGroup(name),
	}
}