title: Migrate one method to System.Text.Json
body: <p>I added NewtonsoftJson as middleware in .net core 3.1. I would love to move over to new System.Text.Json serializer. </p>
  
  <p>I can´t just jump over but is there way to use the one from System.Text.Json in one method some how. More or less it is one that I need to speed up.</p>
  
  <p>Added:
  I have in startup</p>
  
  <pre><code>services.AddControllers(options =&gt; options.RespectBrowserAcceptHeader = true)
          .AddNewtonsoftJson(options =&gt; options.SerializerSettings.ReferenceLoopHandling =
                  Newtonsoft.Json.ReferenceLoopHandling.Ignore);
  </code></pre>
  
  <p>My migration proplem is that I can not just change this to System.Text.Json all at once. So if I could change one controller or just one method in controller to use System.Text.Json version that would solve my problem.</p>