fix workflow version

Author: baronfel

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
     - uses: actions/checkout@v1
     - name: Setup .Net Core
-      uses: actions/setup-dotnet
+      uses: actions/setup-dotnet@v1
       with:
         dotnet-version: ${{matrix.dotnet}}
     - name: Restore tools