如何通过Node.js应用程序正确地输送谷歌云存储资产，以包括缓存头等

const { Storage } = require('@google-cloud/storage');
const express = require('express');

const app = express();

// 设置身份验证
const storage = new Storage({
  keyFilename: 'path/to/keyfile.json',
  projectId: 'your-project-id',
});

// 处理文件上传请求
app.post('/upload', (req, res) => {
  const bucketName = 'your-bucket-name';
  const file = req.file;

  const bucket = storage.bucket(bucketName);
  const fileStream = bucket.file(file.originalname).createWriteStream();

  fileStream.on('error', (err) => {
    console.error(err);
    res.sendStatus(500);
  });

  fileStream.on('finish', () => {
    res.sendStatus(200);
  });

  // 设置缓存头信息
  const metadata = {
    cacheControl: 'public, max-age=3600', // 设置缓存策略
  };

  fileStream.end(file.buffer, metadata);
});

// 处理文件下载请求
app.get('/download', (req, res) => {
  const bucketName = 'your-bucket-name';
  const fileName = 'your-file-name';

  const bucket = storage.bucket(bucketName);
  const file = bucket.file(fileName);

  // 设置缓存头信息
  const metadata = {
    cacheControl: 'public, max-age=3600', // 设置缓存策略
  };

  file.createReadStream()
    .on('error', (err) => {
      console.error(err);
      res.sendStatus(500);
    })
    .pipe(res);
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});