chore: add dotnet-version for Setup .NET Core SDK action

.github/workflows/build.yml

@@ -9,6 +9,9 @@ jobs:
 
       - name: Setup .NET Core SDK
         uses: actions/setup-dotnet@master
+        with:
+          dotnet-version: '6.0.x'
+          include-prerelease: true
       
       - name: Build
         shell: pwsh