feat: push docker image to ghcr (#70)

* Update release.yaml

.github/workflows/release.yaml

@@ -1,3 +1,7 @@
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
 on: release
 name: Build
 jobs:
@@ -106,3 +110,31 @@ jobs:
         EXECUTABLE_NAME: "solidfire-exporter"
         EXECUTABLE_PATH: "./cmd/solidfire-exporter"
         PACKAGE: "./cmd/solidfire-exporter/main.go"
+
+  push_to_registry:
+    name: Push Docker image 
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}