replace netcoreapp project with netstandard2.1

[cbonezzi]

Hey Cesar!
Since you found the solution/workaround for the issue on netstandard2.1 not working with dotnet-ef, please switch the project from netcoreapp2.2 to netstandard2.1.

use the following xml to proceed with the workaround.

make sure to recreate the project as a netstandard project

in csproj add this

netstandard2.1


netcoreapp3.0