我已经设置了API Gateway（HTTP）〉Lambda〉DynamoDB。我可以通过Postman成功地执行PUT和GET请求，但当我尝试通过浏览器执行PUT请求时，收到CORS错误。我可以通过浏览器成功地执行GET请求。
通过浏览器返回的Post请求
Access to XMLHttpRequest at 'https://xxx.execute-api.eu-west-1.amazonaws.com/items' from origin 'http://localhost:5500' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
我已经在API网关上启用了CORS。自动重新部署已打开。我还手动重新部署以防万一。

我还在lambda响应的头中添加了'Access-Control-Allow-Origin'和'Access-Control-Allow-Methods'。我已经尝试了有和没有这些响应的lambda，因为我理解API网关应该解决预检请求。这两种方式都返回CORS 204错误。

const dynamo = new AWS.DynamoDB.DocumentClient();

exports.handler = async (event, context) => {
  let body;
  let statusCode = 200;
  const headers = {
    "Content-Type": "application/json",
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'OPTIONS,PUT,GET'
  };

  try {
    switch (event.routeKey) {
      case "GET /items":
        // database call
      case "PUT /items":
        // databse put
      default:
        throw new Error(`Unsupported route: "${event.routeKey}"`);
    }
  } catch (err) {
    statusCode = 400;
    body = err.message;
  } finally {
    body = JSON.stringify(body);
  }

  return {
    statusCode,
    body,
    headers
  };
};

我相信我应该在Postman中看到我的头，但我没有。我知道API网关正在更新，因为如果我在API网关控制台中删除Access-Control-Allow-Origin，我的GET请求也会因CORS而失败。