[mod] add docker push workflow

.github/workflows/docker-push.yml

@@ -0,0 +1,31 @@
+name: docker-push
+
+on:
+  push:
+    tags:
+    - 'v*'
+
+jobs:
+  push:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Login to DockerHub
+      uses: docker/login-action@v1
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+    - id: get_version
+      uses: battila7/get-version-action@v2
+
+    - name: Build and Push
+      env:
+        REPOSITORY: dohq/dockerhub_ratelimit_exporter
+        VERSION: ${{ steps.get_version.outputs.version-without-v }}
+        DOCKER_BUILDKIT: 1
+      run: |
+        make container_build
+        make container_cache
+        make container_push

.gitignore

@@ -25,3 +25,4 @@
 
 # End of https://www.toptal.com/developers/gitignore/api/go
 dist/
+dockerhub_ratelimit_exporter

Makefile

@@ -1,8 +1,30 @@
+IMAGE_NAME=$(REPOSITORY):$(VERSION)
+LATEST=$(REPOSITORY):latest
+CACHE=$(REPOSITORY):cache-latest
+
+container_build:
+	docker build --cache-from=$(CACHE) \
+		--build-arg=BUILDKIT_INLINE_CACHE=1 \
+		-t $(IMAGE_NAME) \
+		-t $(LATEST) .
+
+container_push:
+	docker push $(IMAGE_NAME)
+	docker push $(CACHE)
+
+# If necessary, add --target
+container_cache:
+	docker build \
+		--target=builder \
+		--build-arg=BUILDKIT_INLINE_CACHE=1 \
+		-t $(CACHE) .
+	docker push $(CACHE)
+
 build:
 	go build
 test:
-	go test -v
+	go test -v -race ./...
 run:
-	go run *.go
+	go run .
 help:
 	go run *.go -h