fix:重置索引

@@ -52,9 +52,10 @@ class Response implements ResponseInterface
      */
     public function getContents(): string
     {
-        $response = clone $this->response;
+        $body = $this->response->getBody();
+        $body->rewind();
 
-        return $response->getBody()->getContents();
+        return $body->getContents();
     }
 
     /**