defmodule Elevator.Timer do
    def keepalive_timer(parent, id, msecs) do
        receive do 
            :keepalive ->
                keepalive_timer(parent, id, msecs)
            
        after
            msecs ->
                send(parent, {:timeout, id})
        end
    end
end

#To run:
# this_pid = self
# spawn fn -> Elevator.Timer.keepalive_timer(this_pid, 1, 5000) end