title: Migrate from /net core 2.1 to .net core 3.1
body: <p>I am getting an error while migrating from .net core 2.1 to .net core 3.1</p>
  
  <p>Error: The Microsoft.AspNetCore.All package is not supported when targeting .NET Core 3.0 or higher.  A FrameworkReference to Microsoft.AspNetCore.The app should be used instead and will be implicitly included by Microsoft.NET.Sdk.Web.</p>