Document sleep(0) warning in README #259

	name: Run Tests
	on:
	push:
	pull_request:
	schedule:
	# Run tests weekly to make sure they keep working despite various
	# dependency changes.
	- cron: '23 06 * * 5'
	workflow_dispatch: # allow running manually
	jobs:
	lua:
	runs-on: ubuntu-latest
	timeout-minutes: 10
	strategy:
	matrix:
	lua: ["5.1", "5.2"]
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-python@v2
	- run: sudo apt install libpcre2-dev
	- run: pip install hererocks
	# Install latest LuaRocks version plus the Lua version for this build job
	# into 'here' subdirectory.
	- run: hererocks here -r^ --lua ${{ matrix.lua }}
	- run: echo $PWD/here/bin >> $GITHUB_PATH
	- run: eval `luarocks path --bin`
	- run: luarocks install luacheck
	- run: luarocks install luacov-coveralls
	- run: luarocks install luaunit
	- run: luarocks install lrexlib-pcre2
	- run: luacheck --globals ngx -- prometheus.lua prometheus_keys.lua prometheus_resty_counter.lua
	- run: luacheck --globals luaunit rex_pcre2 ngx TestPrometheus TestKeyIndex -- prometheus_test.lua
	- run: lua -lluacov prometheus_test.lua
	- run: luacov-coveralls --include ^prometheus
	env:
	COVERALLS_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	# Only report test coverage for lua 5.1 to avoid doing it twice.
	if: ${{ matrix.lua == '5.1' }}
	integration:
	runs-on: ubuntu-latest
	timeout-minutes: 10
	defaults:
	run:
	working-directory: integration
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-go@v2
	with:
	go-version: 1.22
	- run: go get
	- run: ./test.sh

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