public class GetAaddrOutput
{
    public string Ip { get; set; }
    public string pro { get; set; }
    public string proCode { get; set; }
    public string city { get; set; }
    public string cityCode { get; set; }
    public string region { get; set; }
    public string regionCode { get; set; }
    public string addr { get; set; }
    public string regionNames { get; set; }
    public string err { get; set; }
}

var result = await "http://whois.pconline.com.cn/ipJson.jsp?json=true".GetAsAsync<GetAaddrOutput>();

// 返回元组
var (stream, encoding) = await "https://www.furion.icu/".GetAsStreamAsync();

// 包含序列化正常
var result = await "http://whois.pconline.com.cn/ipJson.jsp?json=true".GetAsAsync<GetAaddrOutput>();