f.exs

defmodule TimedThing do
  def thing_that_could_take_a_while(pid) do
    spawn fn() -> 
      0..10_000
      |> Enum.random
      |> Process.sleep
      send pid, :hey_im_done
    end
  end
end

defmodule OtherThing do
  def uh do
    TimedThing.thing_that_could_take_a_while
    reveice do
      :hey_im_done -> IO.puts "its done!"
    after
      10_000 -> IO.puts "it took too long!" 
    end
  end
end