process-2-snippet-9.ex

 def await(%Task{ref: ref} = task, timeout) do
   receive do
     {^ref, reply} ->
       Process.demonitor(ref, [:flush])
       reply
     {:DOWN, ^ref, _, proc, reason} ->
       exit({reason(reason, proc), {__MODULE__, :await, [task, timeout]}})
   after
     timeout ->
       Process.demonitor(ref, [:flush])
       exit({:timeout, {__MODULE__, :await, [task, timeout]}})
   end
 end