ReadCloser: Call close if reader implements it

backend/mem_backend.go

@@ -125,17 +125,21 @@ func memCreate(be *MemoryBackend) (Blob, error) {
 	return blob, nil
 }
 
-// ReadCloser wraps a reader and adds a noop Close method.
+// ReadCloser wraps a reader and adds a noop Close method if rd does not implement io.Closer.
 func ReadCloser(rd io.Reader) io.ReadCloser {
 	return readCloser{rd}
 }
 
-// readCloser wraps a reader and adds a noop Close method.
+// readCloser wraps a reader and adds a noop Close method if rd does not implement io.Closer.
 type readCloser struct {
 	io.Reader
 }
 
 func (rd readCloser) Close() error {
+	if r, ok := rd.Reader.(io.Closer); ok {
+		return r.Close()
+	}
+
 	return nil
 }