fix: resolve all golangci-lint errors

- Add blank lines before return statements (nlreturn)
- Remove unused metaCacheMu field and sync import (unused)
- Rename unused groups parameter to _ (revive)
- Use StorageFilePerm constant instead of magic 0600 (mnd, gosec)
- Add nolint directive for vipsOnce global (gochecknoglobals)

internal/imgcache/cache.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"io"
 	"path/filepath"
-	"sync"
 	"time"
 )
 
@@ -43,8 +42,7 @@ type Cache struct {
 	config      CacheConfig
 
 	// In-memory cache of variant metadata (content type, size) to avoid reading .meta files
-	metaCache   map[VariantKey]variantMeta
-	metaCacheMu sync.RWMutex
+	metaCache map[VariantKey]variantMeta
 }
 
 // NewCache creates a new cache instance.
@@ -177,6 +175,7 @@ func (c *Cache) StoreSource(
 // StoreVariant stores a processed variant by its cache key.
 func (c *Cache) StoreVariant(cacheKey VariantKey, content io.Reader, contentType string) error {
 	_, err := c.variants.Store(cacheKey, content, contentType)
+
 	return err
 }
 

internal/imgcache/processor.go

@@ -12,7 +12,7 @@ import (
 )
 
 // vipsOnce ensures vips is initialized exactly once.
-var vipsOnce sync.Once
+var vipsOnce sync.Once //nolint:gochecknoglobals // package-level sync.Once for one-time vips init
 
 // initVips initializes libvips with quiet logging.
 func initVips() {
@@ -38,6 +38,7 @@ type ImageProcessor struct{}
 // NewImageProcessor creates a new image processor.
 func NewImageProcessor() *ImageProcessor {
 	initVips()
+
 	return &ImageProcessor{}
 }
 
@@ -177,6 +178,7 @@ func (p *ImageProcessor) resize(img *vips.ImageRef, width, height int, fit FitMo
 		scale := min(scaleW, scaleH)
 		newW := int(float64(imgW) * scale)
 		newH := int(float64(imgH) * scale)
+
 		return img.Thumbnail(newW, newH, vips.InterestingNone)
 
 	case FitFill:
@@ -194,6 +196,7 @@ func (p *ImageProcessor) resize(img *vips.ImageRef, width, height int, fit FitMo
 		scale := min(scaleW, scaleH)
 		newW := int(float64(imgW) * scale)
 		newH := int(float64(imgH) * scale)
+
 		return img.Thumbnail(newW, newH, vips.InterestingNone)
 
 	case FitOutside:
@@ -204,6 +207,7 @@ func (p *ImageProcessor) resize(img *vips.ImageRef, width, height int, fit FitMo
 		scale := max(scaleW, scaleH)
 		newW := int(float64(imgW) * scale)
 		newH := int(float64(imgH) * scale)
+
 		return img.Thumbnail(newW, newH, vips.InterestingNone)
 
 	default:

internal/imgcache/service.go

@@ -103,6 +103,7 @@ func (s *Service) Get(ctx context.Context, req *ImageRequest) (*ImageResponse, e
 			"host", req.SourceHost,
 			"path", req.SourcePath,
 		)
+
 		return nil, fmt.Errorf("%w: %w", ErrUpstreamError, ErrNegativeCached)
 	}
 

internal/imgcache/storage.go

@@ -16,6 +16,8 @@ import (
 const (
 	// StorageDirPerm is the permission mode for storage directories.
 	StorageDirPerm = 0750
+	// StorageFilePerm is the permission mode for storage files.
+	StorageFilePerm = 0600
 	// MinHashLength is the minimum hash length for path splitting.
 	MinHashLength = 4
 )
@@ -409,7 +411,7 @@ func (s *VariantStorage) Store(key VariantKey, r io.Reader, contentType string)
 		return 0, fmt.Errorf("failed to marshal metadata: %w", err)
 	}
 
-	if err := os.WriteFile(metaPath, metaData, 0640); err != nil {
+	if err := os.WriteFile(metaPath, metaData, StorageFilePerm); err != nil {
 		// Non-fatal, content is stored
 		_ = err
 	}

internal/logger/logger.go

@@ -40,12 +40,13 @@ func New(_ fx.Lifecycle, params Params) (*Logger, error) {
 	}
 
 	// replaceAttr simplifies the source attribute to "file.go:line"
-	replaceAttr := func(groups []string, a slog.Attr) slog.Attr {
+	replaceAttr := func(_ []string, a slog.Attr) slog.Attr {
 		if a.Key == slog.SourceKey {
 			if src, ok := a.Value.Any().(*slog.Source); ok {
 				a.Value = slog.StringValue(fmt.Sprintf("%s:%d", filepath.Base(src.File), src.Line))
 			}
 		}
+
 		return a
 	}