new Thread(new Runnable() {
            @Override
            public void run() {
                Retrofit retrofit = new Retrofit.Builder()
                        .client(HttpGetUtil.getInstance())
                        .baseUrl("http://xxx.xxx.com/xxx/")
                        .build();

                GitHubService service = retrofit.create(GitHubService.class);
                service.query().enqueue(new Callback<ResponseBody>() {
                    @Override
                    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                        try {
                            response.body().byteStream();
                            String body = response.body().string();//获取返回体的字符串
                            LogUtil.i("****"+body);
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }

                    @Override
                    public void onFailure(Call<ResponseBody> call, Throwable t) {

                    }
                });
            }
        }).start();

public interface GitHubService{
        @POST("app/index")
        Call<ResponseBody> query();
    }