按照微软指令安装：
sdk2.1：https://www.microsoft.com/net/download/linux-package-manager/centos/sdk-current
1. sudo rpm -Uvh https://packages.microsoft.com/config/rhel/7/packages-microsoft-prod.rpm
2. sudo yum update
3. sudo yum install dotnet-sdk-2.1
runtime2.1：https://www.microsoft.com/net/download/linux-package-manager/centos/runtime-current
1. sudo rpm -Uvh https://packages.microsoft.com/config/rhel/7/packages-microsoft-prod.rpm
2. sudo yum update
3. sudo yum install aspnetcore-runtime-2.1
最后验证下是否成功：dotnet --help
