setup-dotnet in Code Scanning workflow

.github/workflows/code-scanning.yml

@@ -14,6 +14,9 @@ on:
     - master
     - V6
 
+env:
+  TGS_DOTNET_VERSION: 8.0.x
+
 concurrency:
   group: "code-scanning-${{ github.head_ref || github.run_id }}-${{ github.event_name }}"
   cancel-in-progress: true
@@ -28,6 +31,11 @@ jobs:
       security-events: write
     if: ${{ vars.TGS_ENABLE_CODE_QL }} == 'true'
     steps:
+    - name: Setup dotnet
+      uses: actions/setup-dotnet@v2
+      with:
+        dotnet-version: '${{ env.TGS_DOTNET_VERSION }}.x'
+
     - name: Checkout
       uses: actions/checkout@v3