.net core在centOS Linux环境下使用HttpClient请求https失败的解决方法

The request was canceled due to the configured HttpClient.Timeout of 100 seconds elapsing.

dotnet core在Linux(如：centOS)环境下使用HttpClient请求https可能会报异常：

One or more errors occurred. (The SSL connection could not be established, see inner exception.) 

设置如下环境变量暂时解决：

export DOTNET_SYSTEM_NET_HTTP_USESOCKETSHTTPHANDLER=0

如果服务器在国外，C#代码访问国内的网站，还有可能是被墙。