fix: 限流提示

revert 引起代码丢失

@@ -8,14 +8,14 @@ exports.serverError = (err, req, res, next) => { // eslint-disable-line
   logger.error(`error at path: ${req.url}`);
   logger.error(`${req.url},${typeof err === 'object' ? JSON.stringify(err) : err}`);
 
-  res.status(err.code || 500);
-
   if (req.xhr) {
     return res.json({
-      code: 500,
-      message: '服务器错误！'
+      code: err.code || 500,
+      message: err.message || '服务器错误！'
     });
   }
 
+  res.status(err.code || 500);
+
   return res.send('服务器开小差了~');
 };