.net core signalR 忽略https 证书

var connection = new hubconnectionbuilder().withurl(serverurl, option =>
             {
                 option.httpmessagehandlerfactory = (handler) =>
                 {
                     var newhandler = handler as httpclienthandler;
                     newhandler.servercertificatecustomvalidationcallback = (request, cert, chain, errors) =>
                     {
                         return true;
                     };
                     return newhandler;
                 };
             }).build();