THttpClient未关闭Delphi中的连接

我的软件包括以下用于发布到URL的功能。我正在使用Sysinternals TCPView查看连接。发布到URL后,连接未关闭。如何更改立即连接关闭的代码?

function PostURL(const AURL: string; Parameters: TStrings): string;
var
  HttpClient: THttpClient;
  HttpResponse: IHttpResponse;
begin
  HttpClient := THTTPClient.Create;
  try
    HttpClient.ConnectionTimeout:=3000;
    HttpClient.ResponseTimeout:=3000;
    HttpResponse := HttpClient.Post(AURL, Parameters, nil, TEncoding.UTF8);
    Result := HttpResponse.ContentAsString();
  finally
    HttpClient.Free;
  end;
end;