Cannot reach salesforce Marketing cloud Rest API from AWS App Runner instance

I am running a spring boot application on AWS App Runner. The application failed to connect to salesforce Marketing cloud Rest API. Here an example of sample code I am trying (which works perfectly in my machine and in another normal EC2).

   String query = "https://xxxxxxxx.auth.marketingcloudapis.com/v2/token";
   String json = "{\n"
            + "\"grant_type\": \"client_credentials\",\n"
            + "\"client_id\": \"xxxxxx\",\n"
            + "\"client_secret\": \"xxxxxx\""
            + "}\n";

    URL url = new URL(query);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setConnectTimeout(10000);
    conn.setReadTimeout(10000);
    conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
    conn.setDoOutput(true);
    conn.setDoInput(true);
    conn.setRequestMethod("POST");

    OutputStream os = conn.getOutputStream();
    os.write(json.getBytes("UTF-8"));
    os.close();

    // read the response
    InputStream in = new BufferedInputStream(conn.getInputStream());
    String text = new BufferedReader(
            new InputStreamReader(in, StandardCharsets.UTF_8))
              .lines()
              .collect(Collectors.joining("\n"));
    System.out.println(text);