title: Add a GET parameter to a POST request with RestSharp
body: <p>I want to make a POST request to a URL like this:</p>
  
  <pre class="lang-none prettyprint-override"><code>http://localhost/resource?auth_token=1234
  </code></pre>
  
  <p>And I want to send JSON in the body. My code looks something like this:</p>
  
  <pre><code>var client = new RestClient("http://localhost");
  var request = new RestRequest("resource", Method.POST);
  request.AddParameter("auth_token", "1234");    
  request.AddBody(json);
  var response = client.Execute(request);
  </code></pre>
  
  <p>How can I set the <code>auth_token</code> parameter to be a GET parameter and make the request as POST?</p>