Add Go lint/vuln tooling and CI checks (#5)

## Summary
- add a root `.golangci.yml` baseline using golangci-lint v2 config
- add `make lint` and `make vuln` targets with binary presence checks
- add a dedicated CI `lint` job running golangci-lint and govulncheck on
pull requests
- add `golangci-lint` and `govulncheck` to the Nix devshell package set
- bump Go toolchain target to 1.25.7 and fix revive findings in
package/blank-import comments

## Validation
- `nix develop -c golangci-lint version`
- `nix develop -c govulncheck -version`
- `make lint`
- `make vuln`
- `GOFLAGS=-mod=vendor go test ./...`
- `GOFLAGS=-mod=vendor go build ./...`

---

<details>
<summary>📋 Implementation Plan</summary>

# Plan: Add Go linting, vulnerability scanning, CI integration, and
devshell tools

## Context / Why
This repository is currently a minimal Go skeleton with CI for
vendoring, tests, and build, but no linting or vulnerability scanning.
The goal is to add a pragmatic, high-signal lint/vuln baseline that:
- runs locally via `make` targets,
- runs in GitHub Actions on PRs,
- and is available in the Nix devshell.

This gives fast feedback early, keeps code quality consistent as the
project grows, and preserves the repo’s existing vendoring conventions.

## Evidence
- **Repo structure + current automation**: Explore report `2dddbb994b`
confirmed:
  - `Makefile` has `vendor/test/build/verify-vendor/codegen` only.
- `.github/workflows/ci.yaml` has one `test` job and vendor
verification.
  - `flake.nix` devshell includes `go`, `gnumake`, `git`, `goreleaser`.
  - `.golangci.yml` and any `govulncheck` usage are absent.
- **Version/pin compatibility**: Explore report `8ffb06210e` validated:
  - `golangci/golangci-lint-action@v9` is current/recommended.
  - `golang/govulncheck-action@v1` is valid/current major.
  - `golangci-lint` v2.x supports planned config keys.
- `pkgs.golangci-lint` and `pkgs.govulncheck` are expected in nixpkgs
unstable.
- **Primary-source action usage**:
  - `https://github.com/golangci/golangci-lint-action`
  - `https://github.com/golang/govulncheck-action`

## Implementation details

### 1) Add root `.golangci.yml` with a strict, low-noise baseline
Create `.golangci.yml` using golangci-lint v2 schema and enforce vendor
mode to align with repo conventions.

```yaml
version: "2"

run:
  timeout: 5m
  modules-download-mode: vendor

linters:
  enable:
    - bodyclose
    - errorlint
    - gofumpt
    - gosec
    - misspell
    - nilerr
    - revive

issues:
  max-issues-per-linter: 0
  max-same-issues: 0

linters-settings:
  gofumpt:
    extra-rules: true
```

Notes:
- Keep default linters enabled
(errcheck/govet/staticcheck/unused/ineffassign/gosimple).
- Start with high-signal extras; avoid deprecated/noisy linters.

### 2) Extend `Makefile` with fail-fast lint/vuln targets
Update `.PHONY` and add targets that assert required binaries exist
before execution.

```makefile
.PHONY: vendor test build verify-vendor codegen lint vuln

lint: $(VENDOR_STAMP)
	@command -v golangci-lint >/dev/null || (echo "golangci-lint not found; use nix develop" && exit 1)
	GOFLAGS=$(GOFLAGS) golangci-lint run ./...

vuln: $(VENDOR_STAMP)
	@command -v govulncheck >/dev/null || (echo "govulncheck not found; use nix develop" && exit 1)
	GOFLAGS=$(GOFLAGS) govulncheck ./...
```

Why this shape:
- Defensive checks produce immediate, actionable failures.
- `GOFLAGS=$(GOFLAGS)` preserves current `-mod=vendor` behavior.

### 3) Integrate lint + vuln checks into `.github/workflows/ci.yaml`
Add a dedicated `lint` job (parallel with `test`) per golangci action
guidance.

```yaml
jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Set up Go
        uses: actions/setup-go@v5
        with:
          go-version-file: go.mod
          cache: true

      - name: Verify vendor is up to date
        run: |
          go mod tidy
          go mod vendor
          git diff --exit-code -- go.mod go.sum vendor/

      - name: Run golangci-lint
        uses: golangci/golangci-lint-action@v9
        with:
          version: v2.8
          args: --timeout=5m ./...

      - name: Run govulncheck
        uses: golang/govulncheck-action@v1
        with:
          go-version-file: go.mod
          go-package: ./...

  test:
    ...
```

Implementation notes:
- Keep existing `test` job logic intact; no behavioral regression for
current checks.
- Use major-version action pinning consistent with current workflow
style.

### 4) Add linter/vuln binaries to `flake.nix` devshell
Extend the `packages` list in the default shell.

```nix
packages = with pkgs; [
  go
  gnumake
  git
  goreleaser
  golangci-lint
  govulncheck
];
```

This guarantees local parity with CI and avoids ad-hoc installs.

## Validation plan
After implementation, run:
1. `nix develop -c golangci-lint version`
2. `nix develop -c govulncheck -version`
3. `make lint`
4. `make vuln`
5. `go test ./...`
6. `go build ./...`

And ensure CI workflow syntax/behavior by opening a PR and confirming
both `lint` and `test` jobs execute successfully.

</details>

---
_Generated with [\`mux\`](https://github.com/coder/mux) • Model:
`openai:gpt-5.3-codex` • Thinking: `xhigh`_

Author: ThomasK33

.github/workflows/ci.yaml

@@ -10,6 +10,41 @@ permissions:
   contents: read
 
 jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          persist-credentials: false
+
+      - name: Set up Go
+        uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5.6.0
+        with:
+          go-version-file: go.mod
+          cache: true
+
+      - name: Verify vendor is up to date
+        run: |
+          go mod tidy
+          go mod vendor
+          git diff --exit-code -- go.mod go.sum vendor/
+
+      - name: Run golangci-lint
+        uses: golangci/golangci-lint-action@1e7e51e771db61008b38414a730f564565cf7c20 # v9
+        with:
+          version: v2.8
+          args: --timeout=5m ./...
+
+      - name: Run golangci-lint formatter checks
+        run: go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.8.0 fmt --diff
+
+      - name: Run govulncheck
+        uses: golang/govulncheck-action@b625fbe08f3bccbe446d94fbf87fcc875a4f50ee # v1
+        with:
+          go-version-file: go.mod
+          go-package: ./...
+
   test:
     runs-on: ubuntu-latest
     steps:
@@ -68,7 +103,7 @@ jobs:
 
   publish-main:
     name: Publish GHCR :main
-    needs: [test, lint-actions]
+    needs: [test, lint, lint-actions]
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     permissions:

.golangci.yml

@@ -0,0 +1,25 @@
+version: "2"
+
+run:
+  timeout: 5m
+  modules-download-mode: vendor
+
+linters:
+  enable:
+    - bodyclose
+    - errorlint
+    - gosec
+    - misspell
+    - nilerr
+    - revive
+
+formatters:
+  enable:
+    - gofumpt
+  settings:
+    gofumpt:
+      extra-rules: true
+
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0

Makefile

@@ -2,7 +2,7 @@ GOFLAGS ?= -mod=vendor
 VENDOR_STAMP := vendor/.modules.stamp
 MODULE_FILES := go.mod $(wildcard go.sum)
 
-.PHONY: vendor test build verify-vendor codegen
+.PHONY: vendor test build lint vuln verify-vendor codegen
 
 $(VENDOR_STAMP): $(MODULE_FILES)
 	go mod tidy
@@ -18,6 +18,15 @@ test: $(VENDOR_STAMP)
 build: $(VENDOR_STAMP)
 	GOFLAGS=$(GOFLAGS) go build ./...
 
+lint: $(VENDOR_STAMP)
+	@command -v golangci-lint >/dev/null || (echo "golangci-lint not found; use nix develop" && exit 1)
+	GOFLAGS=$(GOFLAGS) golangci-lint run ./...
+	GOFLAGS=$(GOFLAGS) golangci-lint fmt --diff
+
+vuln: $(VENDOR_STAMP)
+	@command -v govulncheck >/dev/null || (echo "govulncheck not found; use nix develop" && exit 1)
+	GOFLAGS=$(GOFLAGS) govulncheck ./...
+
 verify-vendor:
 	go mod tidy
 	go mod vendor

flake.lock

@@ -25,6 +25,8 @@
               goreleaser
               actionlint
               zizmor
+              golangci-lint
+              govulncheck
             ];
           };
         }

flake.nix

@@ -1,6 +1,6 @@
 module github.com/coder/coder-k8s
 
-go 1.25.6
+go 1.25.7
 
 require (
 	k8s.io/apimachinery v0.35.0

go.mod

@@ -1,3 +1,4 @@
+// Package controller contains Kubernetes controllers for coder-k8s resources.
 package controller
 
 import (

internal/controller/codercontrolplane_controller.go

@@ -5,8 +5,8 @@
 package deps
 
 import (
-	_ "k8s.io/apimachinery/pkg/runtime"
-	_ "k8s.io/client-go/kubernetes"
-	_ "k8s.io/code-generator"
-	_ "sigs.k8s.io/controller-runtime/pkg/client"
+	_ "k8s.io/apimachinery/pkg/runtime"           // Keep apimachinery runtime dependency vendored.
+	_ "k8s.io/client-go/kubernetes"               // Keep client-go kubernetes client vendored.
+	_ "k8s.io/code-generator"                     // Keep code-generator scripts vendored.
+	_ "sigs.k8s.io/controller-runtime/pkg/client" // Keep controller-runtime client vendored.
 )

internal/deps/deps.go

@@ -1,3 +1,4 @@
+// Package main provides the entrypoint for the coder-k8s binary.
 package main
 
 import (