title: TPL.Dataflow message processing timeout?
body: <p>Using .NET TPL DataFlow blocks.
  Is there any way to timeout the processing of a message?</p>
  
  <p>e.g.</p>
  
  <p>lets say I have a <code>BufferBlock&lt;T&gt;</code>, is it possible to link that to another block that processes one message at a time (<code>MaxDegreeOfParallellism</code> 1) and force a timeout if the processing runs for too long?
  Or is it even possible to do using the BufferBlock only?</p>
  
  <p>I suspect I can use a cancellation token somehow and a delay, but not sure how this would be done.
  Also, how expensive would such timeout be? would it add much overhead to the message processing time?</p>