Update build.yml

Author: mythz

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
       - name: setup .net core
         uses: actions/setup-dotnet@v1.7.2
         with:
-          dotnet-version: 5.0.100
+          dotnet-version: 6.0.100
 
       - name: build
         run: dotnet build