我正在制作一个winforms应用程序，我想同时发送多个HttpWebRequest到我的Https API URL（如20-30个请求），总请求不受限制。然而，经过一段随机时间后，我的Winforms应用程序遇到了问题
error: The underlying connection was closed: An unexpected error occurred on a send
我应该更改代码的哪些部分，以使我的应用程序正确有效地运行，并发送多个HttpWebRequest请求而不会出现问题

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
_tasks = new List<Task>();
cancelSources = new List<CancellationTokenSource>();

foreach (var emailList in smalChunks)
{
    CancellationTokenSource cs = new CancellationTokenSource();
    Task task = Task.Run(async () =>
    {
        await HandleEmailList(emailList, userData, cs);
    }, cs.Token);

    _tasks.Add(task);
    cancelSources.Add(cs);
}
await Task.WhenAll(_tasks.ToArray()).ConfigureAwait(false);

功能波纹管手柄HttpWebRequest

private async Task HandleEmailList(List<SorterResults> emailList, CancellationTokenSource cs)
{
    try
    {
        ar sortUrl = $"http://localhost:5000/api/xxx";

        var httpWebRequest = (HttpWebRequest)WebRequest.Create(sortUrl);
        httpWebRequest.ContentType = "application/json";
        httpWebRequest.Method = "POST";

        using (var streamWriter = new StreamWriter(await httpWebRequest.GetRequestStreamAsync()))
        {
            var jsonData = JsonConvert.SerializeObject(emailList.ToArray());
            var mailData = $"{{\"mails\":{jsonData}}}";
            await streamWriter.WriteAsync(mailData);
        }

        APIResponseData responseResult;
        var httpResponse = (HttpWebResponse)(await httpWebRequest.GetResponseAsync());
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
        {
            var result = await streamReader.ReadToEndAsync();
            responseResult = JsonConvert.DeserializeObject<APIResponseData>(result);
        }
                
        cs.Token.ThrowIfCancellationRequested();
    }
    catch (Exception ex)
    {
        //ex.Message: The underlying connection was closed: An unexpected error occurred on a send
    }
}