Fix sdk

Author: macsux

.github/workflows/dotnet.yaml

@@ -18,7 +18,7 @@ jobs:
       - name: Setup dotnet runtime 2.1.0
         uses: actions/setup-dotnet@v1
         with:
-          dotnet-version: 2.1.300
+          dotnet-version: 2.1.000
       - name: Setup dotnet SDK 3.1
         uses: actions/setup-dotnet@v1
         with: