title: SignalR Core Giving ConnectionId Required Error
body: <p>I'm trying to implement SignalR in my ASP.NET Core 2.0 app -- using SignalR Core Alpha.</p>
  
  <p><a href="https://i.stack.imgur.com/t6sew.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/t6sew.png" alt="enter image description here"></a></p>
  
  <p>When I use Postman to send a simple text to the Hub, I'm getting <code>HttpStatus</code> <code>400</code> with <code>ConnectionId Required</code> error message. In Postman, I tried both <code>GET</code> and <code>POST</code> methods and got the same result.</p>
  
  <p><a href="https://i.stack.imgur.com/rQLyq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rQLyq.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/qRo86.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qRo86.png" alt="enter image description here"></a></p>
  
  <p>I have a very simple method that receives a string -- see below:</p>
  
  <pre><code>public Task Send(string message)
  {
     return Clients.All.InvokeAsync("Send", message);
  }
  </code></pre>
  
  <p>Any idea what's wrong here?</p>