我试图在express.js中显示闪存错误消息，但req.flash(' error ')返回空数组

const express = require('express');
const session = require('express-session');
const flash = require('connect-flash');

const app = express();

app.use(session({
  secret: 'your-secret-key',
  resave: false,
  saveUninitialized: true
}));

app.use(flash());

app.get('/your-route', (req, res) => {
  req.flash('error', 'This is an error message');
  res.redirect('/your-route');
});

<% if (messages.error && messages.error.length > 0) { %>
  <div class="error">
    <% messages.error.forEach(function(error) { %>
      <p><%= error %></p>
    <% }); %>
  </div>
<% } %>