another lint fix + timeout

.golangci.yml

@@ -1,4 +1,6 @@
 version: "2"
+run:
+  timeout: 5m
 linters:
   settings:
     staticcheck:

gcs/public.go

@@ -146,7 +146,7 @@ func (g *PublishedStorage) putFile(path string, source io.Reader, sourceMD5 stri
 	writer := obj.NewWriter(context.TODO())
 
 	if g.storageClass != "" {
-		writer.ObjectAttrs.StorageClass = g.storageClass
+		writer.StorageClass = g.storageClass
 	}
 	if sourceMD5 != "" {
 		writer.Metadata = map[string]string{"Md5": sourceMD5}