Http Client Transport Support

[finishy1995]

For some reason, the API is banned in some countries.

After added the following codes, it works:

        config := gogpt.DefaultConfig("token")
	// 创建一个 HTTP Transport 对象，并设置代理服务器
	proxyUrl, err := url.Parse("http://localhost:{port}")
	if err != nil {
		panic(err)
	}
	transport := &http.Transport{
		Proxy: http.ProxyURL(proxyUrl),
	}
	// 创建一个 HTTP 客户端，并将 Transport 对象设置为其 Transport 字段
	config.HTTPClient = &http.Client{
		Transport: transport,
	}

	c := gogpt.NewClientWithConfig(config)

[eryajf]

Should be integrated into the standard library and used as parameterization

[sashabaranov]

@finishy1995 added this example into README, thank you!

[liuyunzhang]

It is not working, is cause of my proxy？

[liuyunzhang]

It is indeed because my proxy is unstable