limit draining up to 512 bytes from response.Body

Updates #317

github/github.go

@@ -337,8 +337,8 @@ func (c *Client) Do(req *http.Request, v interface{}) (*Response, error) {
 	}
 
 	defer func() {
-		// Drain and close the body to let the Transport reuse the connection
-		io.Copy(ioutil.Discard, resp.Body)
+		// Drain up to 512 bytes and close the body to let the Transport reuse the connection
+		io.CopyN(ioutil.Discard, resp.Body, 512)
 		resp.Body.Close()
 	}()