updated ci.yml

Author: clement911

.github/workflows/ci.yml

@@ -16,6 +16,8 @@ jobs:
     - uses: actions/checkout@v4
     - name: Setup .NET Core SDK
       uses: actions/setup-dotnet@v4
+      with:
+        dotnet-version: '9.0.x'
     - name: Install dependencies
       run: dotnet restore
     - name: Build