如何从函数中连续返回Firebase docChanges实时更新结果？

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.getRealtimeUpdates = functions.https.onRequest((req, res) => {
  const db = admin.firestore();
  const collectionRef = db.collection('your_collection');

  // 监听集合中的文档变化
  const unsubscribe = collectionRef.onSnapshot(snapshot => {
    const docChanges = [];
    snapshot.docChanges().forEach(change => {
      docChanges.push(change.doc.data());
    });

    // 将结果发送回客户端
    res.send(docChanges);
  });

  // 当客户端断开连接时，取消监听
  res.on('close', () => {
    unsubscribe();
  });
});