feat: add golangci-lint for Go code quality

- Add .golangci.yml configuration enabling govet, staticcheck, errcheck, gosimple, ineffassign, unused, gofmt, and goimports linters
- Update scripts/check.sh to run golangci-lint with go vet fallback
- Update CI workflow to install golangci-lint in both format and quality jobs
- Add golangci-lint to CONTRIBUTING.md setup instructions

Closes #266

.github/workflows/check.yml

@@ -27,12 +27,13 @@ jobs:
             ~/Library/Caches/Homebrew
             /usr/local/Cellar/shfmt
             /usr/local/Cellar/shellcheck
-          key: ${{ runner.os }}-brew-quality-${{ hashFiles('**/Brewfile') }}
+            /usr/local/Cellar/golangci-lint
+          key: ${{ runner.os }}-brew-quality-v2-${{ hashFiles('**/Brewfile') }}
           restore-keys: |
-            ${{ runner.os }}-brew-quality-
+            ${{ runner.os }}-brew-quality-v2-
 
       - name: Install tools
-        run: brew install shfmt shellcheck
+        run: brew install shfmt shellcheck golangci-lint
 
       - name: Set up Go
         uses: actions/setup-go@4dc6199c7b1a012772edbd06daecab0f50c9053c # v5
@@ -75,12 +76,18 @@ jobs:
             ~/Library/Caches/Homebrew
             /usr/local/Cellar/shfmt
             /usr/local/Cellar/shellcheck
-          key: ${{ runner.os }}-brew-quality-${{ hashFiles('**/Brewfile') }}
+            /usr/local/Cellar/golangci-lint
+          key: ${{ runner.os }}-brew-quality-v2-${{ hashFiles('**/Brewfile') }}
           restore-keys: |
-            ${{ runner.os }}-brew-quality-
+            ${{ runner.os }}-brew-quality-v2-
 
       - name: Install tools
-        run: brew install shfmt shellcheck
+        run: brew install shfmt shellcheck golangci-lint
+
+      - name: Set up Go
+        uses: actions/setup-go@4dc6199c7b1a012772edbd06daecab0f50c9053c # v5
+        with:
+          go-version: '1.24.6'
 
       - name: Run check script
         run: ./scripts/check.sh --no-format

.golangci.yml

@@ -0,0 +1,56 @@
+# golangci-lint configuration for Mole
+# https://golangci-lint.run/usage/configuration/
+
+run:
+  timeout: 5m
+  # Only lint Go code in cmd directory
+  modules-download-mode: readonly
+
+linters:
+  disable-all: true
+  enable:
+    # Default linters
+    - govet
+    - staticcheck
+    - gosimple
+    - ineffassign
+    - unused
+    # Additional useful linters
+    - errcheck
+    - gofmt
+    - goimports
+
+linters-settings:
+  govet:
+    enable-all: true
+    disable:
+      - fieldalignment # struct field alignment optimization is noisy
+  errcheck:
+    # Don't check for errors on these functions (common patterns)
+    exclude-functions:
+      - (io.Closer).Close
+      - (*os/exec.Cmd).Run
+      - (*os/exec.Cmd).Start
+  staticcheck:
+    checks: ["all"]
+  goimports:
+    local-prefixes: github.com/tw93/Mole
+
+issues:
+  # Don't limit the number of issues per linter
+  max-issues-per-linter: 0
+  max-same-issues: 0
+
+  exclude-rules:
+    # Ignore certain patterns in test files
+    - path: _test\.go
+      linters:
+        - errcheck
+    # Ignore errors from os.Remove in cleanup code
+    - text: "Error return value of `os.Remove` is not checked"
+      linters:
+        - errcheck
+    # Allow unchecked errors on deferred Close calls
+    - text: "Error return value of .*.Close"
+      linters:
+        - errcheck

CONTRIBUTING.md

@@ -4,7 +4,7 @@
 
 ```bash
 # Install development tools
-brew install shfmt shellcheck bats-core
+brew install shfmt shellcheck bats-core golangci-lint
 ```
 
 ## Development

scripts/check.sh

@@ -102,7 +102,27 @@ if [[ "$MODE" != "check" ]]; then
     fi
 fi
 
-echo -e "${YELLOW}3. Running ShellCheck...${NC}"
+echo -e "${YELLOW}3. Running Go linters...${NC}"
+if command -v golangci-lint > /dev/null 2>&1; then
+    if golangci-lint run ./cmd/...; then
+        echo -e "${GREEN}${ICON_SUCCESS} golangci-lint passed${NC}\n"
+    else
+        echo -e "${RED}${ICON_ERROR} golangci-lint failed${NC}\n"
+        exit 1
+    fi
+elif command -v go > /dev/null 2>&1; then
+    echo -e "${YELLOW}${ICON_WARNING} golangci-lint not installed, falling back to go vet${NC}"
+    if go vet ./cmd/...; then
+        echo -e "${GREEN}${ICON_SUCCESS} go vet passed${NC}\n"
+    else
+        echo -e "${RED}${ICON_ERROR} go vet failed${NC}\n"
+        exit 1
+    fi
+else
+    echo -e "${YELLOW}${ICON_WARNING} Go not installed, skipping Go checks${NC}\n"
+fi
+
+echo -e "${YELLOW}4. Running ShellCheck...${NC}"
 if command -v shellcheck > /dev/null 2>&1; then
     if shellcheck mole bin/*.sh lib/*/*.sh scripts/*.sh; then
         echo -e "${GREEN}${ICON_SUCCESS} ShellCheck passed${NC}\n"
@@ -114,7 +134,7 @@ else
     echo -e "${YELLOW}${ICON_WARNING} shellcheck not installed, skipping${NC}\n"
 fi
 
-echo -e "${YELLOW}4. Running syntax check...${NC}"
+echo -e "${YELLOW}5. Running syntax check...${NC}"
 if ! bash -n mole; then
     echo -e "${RED}${ICON_ERROR} Syntax check failed (mole)${NC}\n"
     exit 1
@@ -133,7 +153,7 @@ find lib -name "*.sh" | while read -r script; do
 done
 echo -e "${GREEN}${ICON_SUCCESS} Syntax check passed${NC}\n"
 
-echo -e "${YELLOW}5. Checking optimizations...${NC}"
+echo -e "${YELLOW}6. Checking optimizations...${NC}"
 OPTIMIZATION_SCORE=0
 TOTAL_CHECKS=0