先说一个问题
首先记载一个问题，今天在用 Jenkins 构建项目标时候突然涌现包源的毛病：
/usr/share/dotnet/sdk/2.2.104/NuGet.targets(114,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. [/....csproj]
/usr/share/dotnet/sdk/2.2.104/NuGet.targets(114,5): error : The HTTP request to "GET https://api.nuget.org/v3/index.json" has timed out after 100000ms. [/....csproj]/us
