Use .NET 9

Author: erri120

.github/workflows/ci.yaml

@@ -15,6 +15,11 @@ jobs:
         with:
           submodules: "recursive"
 
+      - name: Setup .NET 9.x
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.x'
+
       - name: Info
         run: dotnet --info
 

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
     "version": "8.0.0",
-    "rollForward": "latestMinor"
+    "rollForward": "latestMajor"
   }
 }