There is a missing case here so this doesn't compile

[rogernordquist-tc]

docs.scala-lang/_overviews/core/futures.md

Line 1184 in 1ae6d88

_ => ()

It should be like:

        completion match {
          case Failure(exception) if exception.getCause != null =>
            println(s"  caused by ${exception.getCause}")
          case _ => ()
        }