Publish Docker snapshot images to ghcr (#116)

diff --git a/.github/workflows/publish-docker.yaml b/.github/workflows/publish-docker.yaml
new file mode 100644
index 0000000..a987c85
--- /dev/null
+++ b/.github/workflows/publish-docker.yaml
@@ -0,0 +1,53 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: publish-docker
+
+on:
+  push:
+    branches:
+      - master
+
+env:
+  SKIP_TEST: true
+  HUB: ghcr.io/apache/skywalking-cli
+
+jobs:
+  build:
+    if: github.repository == 'apache/skywalking-cli'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    timeout-minutes: 30
+    env:
+      VERSION: ${{ github.sha }}
+      APP_NAME: skywalking-cli
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: true
+      - name: Log in to the Container registry
+        uses: docker/login-action@v1.10.0
+        with:
+          registry: ${{ env.HUB }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Build docker image
+        run: |
+          make docker.push || make docker.push
+          docker tag $HUB/$APP_NAME:{$VERSION,latest}
+          docker push $HUB/$APP_NAME:latest
diff --git a/Dockerfile b/Dockerfile
index 264a581..5f9f4a4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+ARG VERSION
+
 FROM golang:1.14 AS builder
 
 ENV CGO_ENABLED=0
diff --git a/Makefile b/Makefile
index bd19b36..a31fde4 100644
--- a/Makefile
+++ b/Makefile
@@ -69,7 +69,7 @@
 		&& cd ..
 
 .PHONY: $(PLATFORMS)
-$(PLATFORMS):
+$(PLATFORMS): clean
 	mkdir -p $(OUT_DIR)
 	GOOS=$(os) GOARCH=$(ARCH) $(GO_BUILD) $(GO_BUILD_FLAGS) -ldflags "$(GO_BUILD_LDFLAGS)" -o $(OUT_DIR)/$(BINARY)-$(VERSION)-$(os)-$(ARCH) cmd/swctl/main.go
 
@@ -150,7 +150,11 @@
 
 .PHONY: docker
 docker:
-	docker build . -t $(HUB)/$(APP_NAME):$(VERSION)
+	docker build --build-arg VERSION=$(VERSION) . -t $(HUB)/$(APP_NAME):$(VERSION)
+
+.PHONY: docker.push
+docker.push: docker
+	docker push $(HUB)/$(APP_NAME):$(VERSION)
 
 .PHONY: test-commands
 test-commands:
diff --git a/README.md b/README.md
index c6cef7e..9e6cb67 100644
--- a/README.md
+++ b/README.md
@@ -49,6 +49,20 @@
 
 You can also copy it to any directory you like, then add that directory to `PATH`. **We recommend you to rename the `swctl-latest-(darwin|linux|windows)-amd64` to `swctl`.**
 
+### Run from Docker image
+
+If you prefer to use Docker, skywalking-cli also provides Docker images for convenient usages since 0.9.0.
+We also push the snapshot Docker images to GitHub registry for developers who want to test the latest features,
+note that this is not Apache releases, and it's for test only, **DO NOT** use it in your production environment.
+
+```shell
+docker run -it --rm apache/skywalking-cli service ls
+
+# Or to use the snapshot Docker image
+
+docker run -it --rm ghcr.io/apache/skywalking-cli/skywalking-cli  service ls
+```
+
 ## Autocompletion
 
 `swctl` provides auto-completion support for bash and powershell, which can save you a lot of typing.
diff --git a/docs/How-to-release.md b/docs/How-to-release.md
index 127e42a..bb42c55 100644
--- a/docs/How-to-release.md
+++ b/docs/How-to-release.md
@@ -185,10 +185,15 @@
 1. Move source codes tar balls and distributions to `https://dist.apache.org/repos/dist/release/skywalking/`, **you can do this only if you are a PMC member**.
 
     ```shell
-    export SVN_EDITOR=vim
-    svn mv https://dist.apache.org/repos/dist/dev/skywalking/cli/$VERSION https://dist.apache.org/repos/dist/release/skywalking/cli
+    svn mv https://dist.apache.org/repos/dist/dev/skywalking/cli/$VERSION https://dist.apache.org/repos/dist/release/skywalking/cli -m"Release SkyWalking CLI $VERSION"
     ```
-    
+
+1. Push Docker images.
+
+```shell
+make docker.push
+```
+
 1. Refer to the previous [PR](https://github.com/apache/skywalking-website/pull/212), update the event and download links on the website.
 
 1. Update [Github release page](https://github.com/apache/skywalking-cli/releases), follow the previous convention.