fix memory leak when there are more than one metric families #3381

	name: Merge check
	on: [ push, pull_request ]
	jobs:
	build:
	name: Merge check
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go 1.18
	uses: actions/setup-go@v1
	with:
	go-version: 1.18
	id: go
	- name: Check out code into the Go module directory
	uses: actions/checkout@v1
	- name: build
	run: \|
	bash -x scripts/build/local.sh
	ut4etcd:
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go 1.18
	uses: actions/setup-go@v1
	with:
	go-version: 1.18
	id: go
	- name: Check out code into the Go module directory
	uses: actions/checkout@v1
	- name: UT-ETCD
	run: \|
	bash -x scripts/ut_test_in_docker.sh etcd
	ut4mongo:
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go 1.18
	uses: actions/setup-go@v1
	with:
	go-version: 1.18
	id: go
	- name: Check out code into the Go module directory
	uses: actions/checkout@v1
	- name: UT-MONGO
	run: \|
	sudo docker compose -f ./scripts/docker-compose.yaml up -d
	sleep 20
	bash -x scripts/ut_test_in_docker.sh mongo
	local:
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go 1.18
	uses: actions/setup-go@v1
	with:
	go-version: 1.18
	id: go
	- name: Check out code into the Go module directory
	uses: actions/checkout@v1
	- name: UT-LOCAL_STORAGE
	run: \|
	rm -rf /data/schemas
	bash -x scripts/ut_test_in_docker.sh local
	integration-test:
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go 1.18
	uses: actions/setup-go@v1
	with:
	go-version: 1.18
	id: go
	- name: Check out code into the Go module directory
	uses: actions/checkout@v1
	- name: Integration Testing
	run: \|
	bash -x scripts/integration_test.sh

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