Lint

BREAKING: Tree interface functions now return errors #26

	name: Lint

	on: [push, pull_request]

	jobs:
	lint:
	runs-on: ubuntu-latest

	env:
	GO_VERSION: "1.21"

	steps:
	- name: Set up Go ${{ env.GO_VERSION }}
	uses: actions/setup-go@v2
	with:
	go-version: ${{ env.GO_VERSION }}

	- name: Check out code
	uses: actions/checkout@v2
	with:
	fetch-depth: 0

	- name: Cache Go modules
	uses: actions/cache@v2
	with:
	path: \|
	~/go/pkg/mod # Module download cache
	~/.cache/go-build # Build cache (Linux)
	key: ${{ runner.os }}-${{ env.GO_VERSION }}-go-${{ hashFiles('**/go.sum') }}
	restore-keys: \|
	${{ runner.os }}-${{ env.GO_VERSION }}-go-

	- name: Check and get dependencies
	run: \|
	go mod tidy
	git diff --exit-code go.mod
	git diff --exit-code go.sum
	go mod download

	- name: golangci-lint
	uses: golangci/golangci-lint-action@v2
	with:
	version: v1.52

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