refactor: use a noop metric implementation if no metrics are provided #552

	# Copyright 2024 The Outline Authors
	#
	# Licensed 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,
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	name: Build and Test

	on:
	push:
	branches: [ master ]
	pull_request:
	branches: [ master ]
	schedule:
	- cron: "0 13 * * *" # Run daily at 1PM UTC.

	permissions: # added using https://github.com/step-security/secure-workflows
	contents: read

	jobs:

	build:
	name: Build
	runs-on: ubuntu-latest
	steps:

	- name: Check out code into the Go module directory
	uses: actions/checkout@v3

	- name: Set up Go
	uses: actions/setup-go@v4
	with:
	go-version-file: '${{ github.workspace }}/go.mod'

	- name: Get dependencies
	run: \|
	# Download GeoIP test data from MaxMind
	git submodule update --init

	- name: Build
	run: go build -v ./...

	- name: Test
	run: go test -race -benchmem -bench=. ./... -benchtime=100ms

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