CI: Go lint using recommended method.

- Remove gotools directory.
- Add golangci's own Github Action.
- Bump image to tkey-builder:4.
- Bump actions/checkout to v4.

.github/workflows/ci.yaml

@@ -13,10 +13,10 @@ jobs:
   ci:
     runs-on: ubuntu-latest
     container:
-      image: ghcr.io/tillitis/tkey-builder:2
+      image: ghcr.io/tillitis/tkey-builder:4
     steps:
       - name: checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           # fetch-depth: 0
           persist-credentials: false
@@ -29,8 +29,5 @@ jobs:
       - name: make
         run: make
 
-      - name: lint go code
-        run: make lint
-
       - name: check for SPDX tags
         run: ./tools/spdx-ensure

.github/workflows/golangci-lint.yml

@@ -0,0 +1,54 @@
+name: golangci-lint
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+  # Optional: allow read access to pull request. Use with `only-new-issues` option.
+  # pull-requests: read
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v4
+        with:
+          go-version: '1.21'
+          cache: false
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          # Require: The version of golangci-lint to use.
+          # When `install-mode` is `binary` (default) the value can be v1.2 or v1.2.3 or `latest` to use the latest version.
+          # When `install-mode` is `goinstall` the value can be v1.2.3, `latest`, or the hash of a commit.
+          version: v1.55.2
+
+          # Optional: working directory, useful for monorepos
+          # working-directory: somedir
+
+          # Optional: golangci-lint command line arguments.
+          #
+          # Note: By default, the `.golangci.yml` file should be at the root of the repository.
+          # The location of the configuration file can be changed by using `--config=`
+          # args: --timeout=30m --config=/my/path/.golangci.yml --issues-exit-code=0 
+
+          # Optional: show only new issues if it's a pull request. The default value is `false`.
+          # only-new-issues: true
+
+          # Optional: if set to true, then all caching functionality will be completely disabled,
+          #           takes precedence over all other caching options.
+          # skip-cache: true
+
+          # Optional: if set to true, then the action won't cache or restore ~/go/pkg.
+          # skip-pkg-cache: true
+
+          # Optional: if set to true, then the action won't cache or restore ~/.cache/go-build.
+          # skip-build-cache: true
+
+          # Optional: The mode to install golangci-lint. It can be 'binary' or 'goinstall'.
+          # install-mode: "goinstall"

Makefile

@@ -1,12 +1,6 @@
 all:
 	go build
 
-.PHONY: lint
-lint:
-	$(MAKE) -C gotools
-	GOOS=linux   ./gotools/golangci-lint run
-	GOOS=windows ./gotools/golangci-lint run
-
 .PHONY: spdx
 spdx:
 	./tools/spdx-ensure