request logger: add example for Slog https://pkg.go.dev/log/slog (#2543)

middleware/request_logger.go

@@ -8,6 +8,30 @@ import (
 	"github.com/labstack/echo/v4"
 )
 
+// Example for `slog` https://pkg.go.dev/log/slog
+// 	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
+//	e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
+//		LogStatus:   true,
+//		LogURI:      true,
+//		LogError:    true,
+//		HandleError: true, // forwards error to the global error handler, so it can decide appropriate status code
+//		LogValuesFunc: func(c echo.Context, v middleware.RequestLoggerValues) error {
+//			if v.Error == nil {
+//				logger.LogAttrs(context.Background(), slog.LevelInfo, "REQUEST",
+//					slog.String("uri", v.URI),
+//					slog.Int("status", v.Status),
+//				)
+//			} else {
+//				logger.LogAttrs(context.Background(), slog.LevelError, "REQUEST_ERROR",
+//					slog.String("uri", v.URI),
+//					slog.Int("status", v.Status),
+//					slog.String("err", v.Error.Error()),
+//				)
+//			}
+//			return nil
+//		},
+//	}))
+//
 // Example for `fmt.Printf`
 // 	e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
 //		LogStatus:   true,