Answer by Weiwei Cai - MSFT for Trouble compiling using a MyGet package in .NET Core project

Please pack .NET Core packages with following script code added in project.json file.

"scripts": {
"postcompile": [
  "dotnet pack --no-build --configuration %compile:Configuration%"
  ]
}

After compile your .NET Core project, it will generate .nupck file in \bin\debug file. Then please upload this package to your NuGet feed and install it on your project.

If I pack the .NET Core packages with your steps that using nuspec file, I get the same issue with you. The .NET Core project is different with common project, which is manager packages with project.json. So please pack your .NET Core packages with project.josn file.