var client = new RestClient(url);
            client.Timeout = -1;
            var request = new RestRequest(Method.POST);
            client.UserAgent = "Apifox/1.0.0 (https://apifox.com)";
            request.AddHeader("Content-Type", "application/json");
            //request.AddHeader("Authorization", "Bearer 123");
            var body = @JsonData;

            request.AddParameter("application/json", body, ParameterType.RequestBody);
            IRestResponse response = client.Execute(request);

这是我的API调用代码，然后一开始提示：由于远程方已关闭传输流,身份验证失败。
我以为是因为Https 的原因：
所以添加代码来忽略SSL证书但是还是不行

ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) => true;

于是想想应该可能是http协议的问题
于是

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;

问题成功解决

分析原因应该是.Net 4.6以下版本协议固定的原因，升级.Net框架版本可以解决，或者可以上方指定协议的代码也可以解决