update go-version to 1.21, add build & push docker workflow #1

	name: 'build & push docker staging'

	on:
	pull_request_target:
	branches: [main]
	types:
	- closed

	jobs:
	if_merged:
	if: github.event.pull_request.merged == true
	runs-on: ubuntu-latest
	steps:
	- name: Checkout
	uses: actions/checkout@v4

	- name: Set up QEMU
	uses: docker/setup-qemu-action@v3

	- name: Set up Docker Buildx
	uses: docker/setup-buildx-action@v3

	- name: Setup golang environment
	uses: actions/setup-go@v4
	with:
	go-version: '1.21'

	- name: Install dependencies
	run: go mod tidy

	- name: Log in to Docker Hub
	uses: docker/login-action@v3
	with:
	registry: ${{ secrets.DOCKER_ENDPOINT }}
	username: ${{ secrets.DOCKER_USERNAME }}
	password: ${{ secrets.DOCKER_PASSWORD }}

	- name: set build env variables
	shell: bash
	run: \|
	REPO_VERSION=$(git rev-parse --git-dir > /dev/null 2>&1 && git fetch -q origin --tags && git describe --always --dirty --tags)
	REPO_REV=$(git rev-parse --git-dir > /dev/null 2>&1 && git rev-parse HEAD 2>/dev/null)
	BUILD_DATE=$(date -u +%FT%T)
	echo "REPO_VERSION=$REPO_VERSION" >> $GITHUB_ENV
	echo "REPO_REV=$REPO_REV" >> $GITHUB_ENV
	echo "BUILD_DATE=$BUILD_DATE" >> $GITHUB_ENV

	- name: Build and push
	uses: docker/build-push-action@v5
	with:
	context: .
	platforms: linux/amd64,linux/arm64
	push: true
	build-args: \|
	VERSION=${{ env.REPO_VERSION }}
	REPO_REV=${{ env.REPO_REV }}
	DATE=${{ env.BUILD_DATE }}
	tags: ${{ secrets.DOCKER_ENDPOINT }}${{ secrets.DOCKER_REPO }}/fishymetrics:${{ env.REPO_VERSION }}

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