GHA workflow: publish to NuGet on tag

Author: askazakov

.github/workflows/publish.yml

@@ -7,5 +7,18 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     steps:
-      - id: echo
-        run: echo "hello $GITHUB_REF"
+      - uses: actions/setup-dotnet@v1
+      - uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.release.tag_name }}
+          fetch-depth: 0
+      - run: dotnet build --configuration Release
+      - name: pack
+        run: > 
+          dotnet pack mongo-declarative-indexes/mongo-declarative-indexes.csproj \
+                      --no-build \
+                      --configuration Release \
+                      -p:PackageVersion=${{ github.event.release.tag_name }} \
+                      --output .
+      - name: push
+        run: dotnet nuget push *.nupkg --source https://api.nuget.org/v3/index.json --api-key ${{secrets.NUGET_API_KEY}}