fix race in test setup/teardown #73

	name: Build and test

	on: [push, pull_request, workflow_dispatch]

	jobs:
	build-test:
	runs-on: ubuntu-latest
	strategy:
	max-parallel: 1 # cannot run tests concurrently, files are created
	matrix:
	go-version: ['stable', 'oldstable']
	steps:
	- uses: actions/checkout@v3

	- uses: actions/setup-go@v4
	with:
	go-version: ${{ matrix.go-version }}
	- run: make build

	# Need to run tests with a temp dir on same file system for os.Rename to succeed.
	- run: 'mkdir -p tmp && TMPDIR=$PWD/tmp make test'

	- uses: actions/upload-artifact@v3
	with:
	path: cover.html

	# Rebuild webmail frontend code, should be the same as committed.
	- uses: actions/setup-node@v3
	with:
	node-version: 16
	cache: 'npm'
	- run: npm ci
	- run: 'touch webmail/*.ts && make frontend'

	# Format code, we check below if nothing changed.
	- run: 'make fmt'

	# Enforce the steps above didn't make any changes.
	- run: git diff --exit-code

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