Update main.yml

Author: mgravell

.github/workflows/main.yml

@@ -42,6 +42,8 @@ jobs:
       uses: actions/checkout@v1
     - name: Setup dotnet
       uses: actions/setup-dotnet@v4
+      with:
+        dotnet-version: '9.0.x'
     - name: .NET Build
       run: dotnet build Build.csproj -c Release /p:CI=true
     - name: Dapper Tests