I use this code to send but during the execution it hangs indefinitely on PublishAsync.
What is the reason? How to fix it?

我使用此代码进行发送，但在执行过程中，它在PublishAsync上无限期挂起。原因是什么？如何修复它？

using System;

using Amazon.SimpleNotificationService;
using Amazon.SimpleNotificationService.Model;
using System.Threading.Tasks;

namespace ConsoleApp4
{
    class Program
    {
        static void Main(string[] args)
        {
            var client = new AmazonSimpleNotificationServiceClient(Amazon.RegionEndpoint.USEast2);
            SendMessage(client).Wait();
        }

        static async Task SendMessage(IAmazonSimpleNotificationService snsClient)
        {
            var request = new PublishRequest
            {
                TopicArn = "INSERT TOPIC ARN",
                Message = "Test Message"
            };

            await snsClient.PublishAsync(request);
        }
    }

This function hangs in WinForms app:

此函数在WinForms应用程序中挂起：

 public async Task<string> PublishMessageHandler103(string messageText, string msgGroup)
 {
     try
     {
         string topicArn = topicarn;
         var awsCredentials = new Amazon.Runtime.BasicAWSCredentials(accKey, secKey);
         var client = new Amazon.SimpleNotificationService.AmazonSimpleNotificationSer‌​viceClient(awsCreden‌​tials, regionEndpoint);
         var request = new PublishRequest
         {
             TopicArn = topicArn,
             Message = messageText,
             MessageGroupId = msgGroup
         };
         var response = await client.PublishAsync(request);// <----Hangs
         Console.WriteLine($"Successfully published message ID: {response.MessageId}");
         return $"Message Published: {msg}";
     }
     catch (Exception ex)
     {
         Console.WriteLine("\n\n{0}", ex.Message);
     }
     return "Hmmm";
 }

This .NET code looks fine. I just executed this C# code in Visual Studio and it worked fine.

这段.NET代码看起来不错。我刚刚在Visual Studio中执行了这段C#代码，它工作得很好。

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX - License - Identifier: Apache - 2.0

namespace PublishToSNSTopicExample
{
    // snippet-start:[SNS.dotnetv3.PublishToSNSTopicExample]
    using System;
    using System.Threading.Tasks;
    using Amazon.SimpleNotificationService;
    using Amazon.SimpleNotificationService.Model;

    /// <summary>
    /// This example publishes a message to an Amazon Simple Notification
    /// Service (Amazon SNS) topic. The code uses the AWS SDK for .NET and
    /// .NET Core 5.0.
    /// </summary>
    public class PublishToSNSTopic
    {
        public static async Task Main()
        {
            string topicArn = "arn:aws:sns:us-east-1:814548047983:scott1111";
            string messageText = "This is an example message to publish to the ExampleSNSTopic.";

            IAmazonSimpleNotificationService client = new AmazonSimpleNotificationServiceClient();

            await PublishToTopicAsync(client, topicArn, messageText);
        }

        /// <summary>
        /// Publishes a message to an Amazon SNS topic.
        /// </summary>
        /// <param name="client">The initialized client object used to publish
        /// to the Amazon SNS topic.</param>
        /// <param name="topicArn">The ARN of the topic.</param>
        /// <param name="messageText">The text of the message.</param>
        public static async Task PublishToTopicAsync(
            IAmazonSimpleNotificationService client,
            string topicArn,
            string messageText)
        {
            var request = new PublishRequest
            {
                TopicArn = topicArn,
                Message = messageText,
            };

            var response = await client.PublishAsync(request);

            Console.WriteLine($"Successfully published message ID: {response.MessageId}");
        }
    }
    // snippet-end:[SNS.dotnetv3.PublishToSNSTopicExample]
}

Check the ARN of the topic and check your network connectivity. The .NET code works. You can find this example and others for this service in the AWS Code Library.

检查主题的ARN并检查您的网络连接。.NET代码可以正常工作。您可以在AWS代码库中找到该服务的此示例和其他示例。

Amazon SNS examples using AWS SDK for .NET

使用AWS SDK for.NET的Amazon SNS示例

UPDATE

更新

I just noticed something about your code. You use:

我刚注意到你的代码有点问题。您可以使用：

SendMessage(client).Wait();

SendMessage(客户端).Wait()；

In AWS example, its:

在AWS示例中，其：

await PublishToTopicAsync(client, topicArn, messageText);

等待PublishToTopicAsync(客户端，topicArn，MessageText)；

For Windows Forms

对于Windows窗体

 var response = await client.PublishAsync(request);// <----Hangs

and this way works fine

而且这种方式很好用

 var response = await client.PublishAsync(request).ConfigureAwait(false);//OK!