title: Why does JsonSerializer give empty?
body: <p>Given this class, I am trying to serialize but it isn't working.</p>
  
  <pre><code>using System.Text.Json;
  public class Service
  {
      public Service() { }
      public string service;
      public string description;
  }
  
          Service c = new Service();
          c.description = "desc";
          c.service = "serv";
          string x = JsonSerializer.Serialize&lt;Service&gt;(c);
  </code></pre>
  
  <p>Debugging I see x == "{}".  What am I missing?</p>
  
  <p>C# .net core 3.1</p>