Nodejs 后端在 Google Cloud 上收到 500 服务器错误

Question

尝试启动并运行我们的小型应用项目的后端。部署后从谷歌云服务器获取 500 服务器错误。

这是 server.js 文件：

const express = require('express');
const cors = require('cors');
const mongoose = require('mongoose');
const passport = require('passport');

require('dotenv').config();

const app = express();
const port = process.env.PORT || 8080;

app.use(passport.initialize());
app.use(cors());
app.use(express.json());
app.use(express.urlencoded({extended: true}));

const uri = process.env.ATLAS_URI;
mongoose.connect(uri, { useNewUrlParser: true, useCreateIndex: true, useUnifiedTopology: true, useFindAndModify: false  }
);
const connection = mongoose.connection;
connection.once('open', () => {
  console.log("MongoDB database connection established successfully");
})

const completedRouter = require('./routes/completed')
const authRouter = require('./routes/api/users');
const questionRouter = require('./routes/questions');
//const completedRouter = require('./routes/completed');
require("./config/passport")(passport);

app.use('/completed', completedRouter)
app.use('/api/users', authRouter)
app.use('/questions', questionRouter);
app.use('/completed', completedRouter);

app.listen(port, () => {
    console.log(`Server is running on port: ${port}`);
});

还有 app.yaml 文件：

runtime: nodejs14

env_variables: 
ATLAS_URI= <OUR MONGO DB URI CONNECTION STRING>
CLIENT_URL=http://localhost:3000