<PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="10.0.0-rc.2.25502.107" />

System.Diagnostics.CodeAnalysis.DisallowNullAttribute

Specifies that null is disallowed as an input even if the corresponding type allows it.
namespace System.Diagnostics.CodeAnalysis { internal sealed class DisallowNullAttribute : Attribute { public DisallowNullAttribute(); } }