title: BeginInvoke not supported on .NET core? (PlatformNotSupported exception)
body: <p>I've ported a library FluentFTP to .NET standard/.NET core but the async methods use BeginInvoke within an async/await block. So its something like this:</p>
  
  <pre><code>async ConnectAsync(){
     BeginConnect();
  }
  void BeginConnect(){
     BeginInvoke(...)   &lt;&lt; error at this point
  }
  </code></pre>
  
  <p>At that point I get a PlatformNotSupported exception. What can be done to support this on .NET core? </p>
  
  <ul>
  <li>Full info <a href="https://github.com/hgupta9/FluentFTP/issues/142#issuecomment-316120234" rel="noreferrer">here</a>.</li>
  <li>Full code here: <a href="https://github.com/hgupta9/FluentFTP/blob/master/FluentFTP/Client/FtpClient_Connection.cs#L1236" rel="noreferrer">ConnectAsync</a>, <a href="https://github.com/hgupta9/FluentFTP/blob/master/FluentFTP/Client/FtpClient_Connection.cs#L1210" rel="noreferrer">BeginConnect</a>.</li>
  </ul>