You did set the [`IncludeSymbols`](https://github.com/MintPlayer/MintPlayer.Dotnet.Tools/blob/master/SeasonChecker/MintPlayer.SeasonChecker/MintPlayer.SeasonChecker.csproj#L21) property. However the symbol packages are not published to [nuget.org](https://www.nuget.org/packages/MintPlayer.SeasonChecker) for [your package](https://www.nuget.org/packages/DiffPatch/)  You could do this automatically [like this](https://github.com/MintPlayer/MintPlayer.Dotnet.Tools/blob/master/.github/workflows/dotnet-build-master.yml#L53)