use io.NopCloser replace closeWrapper (#20287)

cmd/bitrot-streaming.go

@@ -141,13 +141,7 @@ func (b *streamingBitrotReader) Close() error {
 	}
 	if closer, ok := b.rc.(io.Closer); ok {
 		// drain the body for connection reuse at network layer.
-		xhttp.DrainBody(struct {
-			io.Reader
-			io.Closer
-		}{
-			Reader: b.rc,
-			Closer: closeWrapper(func() error { return nil }),
-		})
+		xhttp.DrainBody(io.NopCloser(b.rc))
 		return closer.Close()
 	}
 	return nil

cmd/xl-storage.go

@@ -2079,14 +2079,6 @@ func (s *xlStorage) ReadFileStream(ctx context.Context, volume, path string, off
 	return &sendFileReader{Reader: io.LimitReader(file, length), Closer: file}, nil
 }
 
-// closeWrapper converts a function to an io.Closer
-type closeWrapper func() error
-
-// Close calls the wrapped function.
-func (c closeWrapper) Close() error {
-	return c()
-}
-
 // CreateFile - creates the file.
 func (s *xlStorage) CreateFile(ctx context.Context, origvolume, volume, path string, fileSize int64, r io.Reader) (err error) {
 	if origvolume != "" {