title: Request.HttpContext.Connection.ClientCertificate is always null
body: <p>I have an ASP.Net core website deployed on Azure app service for Linux. </p>
  
  <p>In the controller, I am trying to get the client certificate like below:</p>
  
  <pre><code>var callerCertificate = Request.HttpContext.Connection.ClientCertificate;
  </code></pre>
  
  <p>I always get <code>callerCertificate</code> as <em>null</em>. 
  I have tried <code>await Request.HttpContext.Connection.GetClientCertificateAsync()</code> with same result <em>null</em>.</p>
  
  <p>My website webhost creation looks like below:</p>
  
  <pre><code>WebHost.CreateDefaultBuilder(args)
                  .UseKestrel()
                  .UseStartup&lt;Startup&gt;()
                  .UseSerilog();
  </code></pre>
  
  <p>I have also set SSL setting for the website (in Azure) as below:</p>
  
  <p><a href="https://i.stack.imgur.com/lOMLl.png" rel="noreferrer"><img src="https://i.stack.imgur.com/lOMLl.png" alt="enter image description here"></a></p>
  
  <p>The client side caller is a net462 project that uses <code>Microsoft.Rest.CertificateCredentials</code> to set the certificate to HTTP request.</p>
  
  <pre><code>var cred = new CertificateCredentials(_deviceCertificate)
  ...
  await this.cred.ProcessHttpRequestAsync(_httpRequest, cancellationToken).ConfigureAwait(false);
  </code></pre>