gh: add code coverage #166

	name: Test fastwalk on Linux
	on:
	push:
	branches: [master]
	pull_request:
	branches: [master]
	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	# Test all supported versions on Linux (since it's fast)
	matrix:
	go: ['1.20', '1.21', '1.22', '1.23']
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 1
	- name: Set up Go
	uses: actions/setup-go@v5
	with:
	go-version: ${{ matrix.go }}
	- name: Test
	run: go test -covermode=count -coverprofile=coverage.txt -race ./...
	- name: Test Builds
	run: make test_build --jobs=4
	- name: Upload coverage reports to Codecov
	uses: codecov/codecov-action@v5
	with:
	token: ${{ secrets.CODECOV_TOKEN }}

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