Update dotnetcore.yml (#159)

Author: ardalis

.github/workflows/dotnetcore.yml

@@ -21,7 +21,7 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v3
       with:
-          dotnet-version: '7.x'
+          dotnet-version: '8.x'
     - name: Install dependencies
       run: dotnet restore
     - name: Build