HttpLib使用
https://github.com/j6mes/httplib/
https://www.cnblogs.com/haogj/archive/2013/01/02/2842265.html
参考文档：
https://docs.microsoft.com/en-us/dotnet/csharp/async
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/async/index
原文：https://www.cnblogs.com/legion/p/9722313.html