Dio添加Cookie

在使用Options添加headers時，Map沒有定義內部類型：

    Dio dio = new Dio(); Map headers = new Map(); headers['Cookie'] = cookie; Options options = new Options( headers:headers ); Future response; response = dio.get(url,options: options); 

結果請求一直失敗，添加上Map內部類型的定義，請求成功。

    Dio dio = new Dio(); Map<String, dynamic> headers = new Map(); headers['Cookie'] = cookie; Options options = new Options( headers:headers ); Future response; response = dio.get(url,options: options);