CentOS 7.4 下安裝.net core 2.1，參考瞭如下兩個頁面：
https://www.microsoft.com/net/download/linux-package-manager/centos/sdk-current
https://docs.microsoft.com/zh-cn/dotnet/core/linux-prerequisites?tabs=netcore2x
具體指令如下：
sudo rpm -Uvh https://packages.microsoft.com/config/rhel/7/packages-microsoft-prod.rpm
sudo yum update
sudo yum install dotnet-sdk-2.1