Error: Request failed with status code 502 with aws lambda aws api gateway

为什么我在使用 aws lambda 函数和 aws api 网关时会收到错误 502 这是我来自 linktokenfunction.js 的代码：

var express = require('express');
var bodyParser = require('body-parser');
var awsServerlessExpressMiddleware = require('aws-serverless-express/middleware');
const {Configuration, PlaidApi, PlaidEnvironments} = require('plaid');

var app = express();
app.use(bodyParser.json());
app.use(awsServerlessExpressMiddleware.eventContext());

app.use(function (req, res, next) {
  res.header('Access-Control-Allow-Origin', '*');
  res.header(
    'Access-Control-Allow-Headers',
    'Origin, X-Requested-With, Content-Type, Accept',
  );
  next();
});

const configuration = new Configuration({
  basePath: PlaidEnvironments.sandbox,
  baseOptions: {
    headers: {
      'PLAID-CLIENT-ID': '...',
      'PLAID-SECRET': '...',
      'PLAID-VERSION': '2020-09-14',
    },
  },
});

const client = new PlaidApi(configuration);

app.post('/plaidLinkToken', async function (request, response, next) {
  const clientUserId = JSON.parse(request.body);

  const data = client.linkTokenCreate({
    user: {
      client_user_id: clientUserId,
    },
    client_name: '...',
    products: ['auth', 'transactions'],
    country_codes: ['US'],
    language: 'en',
  });

  const link_token = data.link_token;
  response.json({link_token: link_token});
});

module.exports = app;

这是我的按钮添加卡：

const CardScreen = ({navigation}: any) => {
  const [user, setUser] = useState(null);
  const [linkToken, setLinkToken] = useState('');
  const [showLinkCardModal, setShowLinkCardModal] = useState(false);

  async function getLinkToken() {
    let token = await API.post(
      'linktokenapi',
      '/plaidLinkToken',
      user?.attributes.id,
    );
    token = token.link_token;
    setLinkToken(token);
    setShowLinkCardModal(true);
  }

  useEffect(() => {
    getUser();
  }, []);

  return (
    <View style={styles.cardContainer}>
      <View>
        <Text style={styles.userName}>
          {user?.attributes.given_name} {user?.attributes.family_name}
        </Text>
      </View>
      <View>
        <TouchableOpacity onPress={getLinkToken}>
          <Text>Link a new card</Text>
        </TouchableOpacity>
        {showLinkCardModal && <PlaidButton token={linkToken}/>}
      </View>
    </View>
  );
};

我对 aws 服务和云很陌生，但为什么会出现此错误以及如何解决此问题？

无法发布问题，因为代码太多，所以我不得不删除其中的几个。