chore: auto build docker image for web

.github/workflows/build.yml

@@ -0,0 +1,35 @@
+name: build on tag
+
+on:
+  push:
+    branches: [ web ]
+  pull_request:
+    branches: [ web ]
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    name: Build
+    steps:
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v2
+    - name: Set output
+      id: vars
+      run: echo ::set-output name=tag::${GITHUB_REF#refs/*/}
+    - name: Set up QEMU
+      uses: docker/setup-qemu-action@v1
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v1
+    - name: Login to Docker Hub
+      uses: docker/login-action@v1
+      with:
+        username: ${{ secrets.DOCKER_HUB_USERNAME }}
+        password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+    - name: Build and push
+      id: docker_build
+      uses: docker/build-push-action@v2
+      with:
+        push: true
+        tags: ${{ secrets.DOCKER_HUB_USERNAME }}/go-
+    - name: Image digest
+      run: echo ${{ steps.docker_build.outputs.digest }}