res_levis_backend/internal/pkg/logger/logger.go

package logger

import (
	"io"
	"log/slog"
	"os"
)

// CreateLogger creates a logger writing to both stderr and the given file.
// If the file cannot be opened, returns a logger that writes only to stderr and a no-op cleanup.
// Callers can check whether logging to file is active if needed.
func CreateLogger(fname string) (*slog.Logger, func()) {
	f, err := os.OpenFile(fname, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		return slog.New(slog.NewJSONHandler(os.Stderr, nil)), func() {}
	}
	w := io.MultiWriter(os.Stderr, f)
	logger := slog.New(slog.NewJSONHandler(w, nil))
	cleanup := func() { f.Close() }
	return logger, cleanup
}