[#308] Fix linter issues

Signed-off-by: Alex Vanin <a.vanin@yadro.com>

api/cache/listsession.go

@@ -48,7 +48,7 @@ func (k *ListSessionKey) String() string {
 
 // NewListSessionCache is a constructor which creates an object of ListObjectsCache with the given lifetime of entries.
 func NewListSessionCache(config *Config) *ListSessionCache {
-	gc := gcache.New(config.Size).LRU().Expiration(config.Lifetime).EvictedFunc(func(key interface{}, val interface{}) {
+	gc := gcache.New(config.Size).LRU().Expiration(config.Lifetime).EvictedFunc(func(_ interface{}, val interface{}) {
 		session, ok := val.(*data.ListSession)
 		if !ok {
 			config.Logger.Warn(logs.InvalidCacheEntryType, zap.String("actual", fmt.Sprintf("%T", val)),

api/handler/copy.go

@@ -129,15 +129,15 @@ func (h *handler) CopyObjectHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	var dstSize uint64
-	if srcSize, err := layer.GetObjectSize(srcObjInfo); err != nil {
+	srcSize, err := layer.GetObjectSize(srcObjInfo)
+	if err != nil {
 		h.logAndSendError(w, "failed to get source object size", reqInfo, err)
 		return
-	} else if srcSize > layer.UploadMaxSize { //https://docs.aws.amazon.com/AmazonS3/latest/API/API_CopyObject.html
+	} else if srcSize > layer.UploadMaxSize { // https://docs.aws.amazon.com/AmazonS3/latest/API/API_CopyObject.html
 		h.logAndSendError(w, "too bid object to copy with single copy operation, use multipart upload copy instead", reqInfo, errors.GetAPIError(errors.ErrInvalidRequestLargeCopy))
 		return
-	} else {
-		dstSize = srcSize
 	}
+	dstSize = srcSize
 
 	args, err := parseCopyObjectArgs(r.Header)
 	if err != nil {

api/handler/multipart_upload_test.go

@@ -180,7 +180,7 @@ func TestMultipartUploadSize(t *testing.T) {
 		equalDataSlices(t, data[partSize:], part)
 	})
 
-	t.Run("check correct size when part copy", func(t *testing.T) {
+	t.Run("check correct size when part copy", func(_ *testing.T) {
 		objName2 := "obj2"
 		uploadInfo := createMultipartUpload(hc, bktName, objName2, headers)
 		sourceCopy := bktName + "/" + objName