add nightly docker build workflows

Signed-off-by: R.I.Pienaar <rip@devco.net>

.github/workflows/nightly.yaml

@@ -0,0 +1,36 @@
+name: NATS Server Nightly
+on:
+  schedule:
+    - cron: "0 40 * * *"
+
+jobs:
+  nightly_release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v1
+
+      - name: Setup Go
+        uses: actions/setup-go@v1
+        with:
+          go-version: 1.14
+
+      - name: goreleaser
+        uses: goreleaser/goreleaser-action@v2
+        with:
+          version: latest
+          args: release --snapshot --config .goreleaser-nightly.yml
+
+      - name: images
+        run: |
+          docker images
+
+      - name: docker_login
+        run: |
+          docker login -u "${{ secrets.DOCKER_USERNAME }}" -p "${{ secrets.DOCKER_PASSWORD }}"
+
+      - name: docker_push
+        run: |
+          NDATE=$(date +%Y%m%d)
+          docker push synadia/nats-server:nightly-${NDATE}
+          docker push synadia/nats-server:nightly