当我在Node.js中使用集群时，如何一次运行中间件功能

const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);

  // Fork workers
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  cluster.on('exit', (worker, code, signal) => {
    console.log(`Worker ${worker.process.pid} died`);
  });
} else {
  console.log(`Worker ${process.pid} started`);

  // 运行中间件功能
  const express = require('express');
  const app = express();

  // 添加中间件
  app.use((req, res, next) => {
    // 中间件逻辑
    console.log('Middleware executed');
    next();
  });

  // 添加路由
  app.get('/', (req, res) => {
    res.send('Hello, World!');
  });

  // 启动服务器
  const server = http.createServer(app);
  server.listen(3000, () => {
    console.log('Server started on port 3000');
  });
}