gen_server_terminate.exs

defmodule MyServer do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def kill do
    GenServer.cast(__MODULE__, :stop)
  end

  def handle_cast(request, state) do
    case request do
      :stop -> {:stop, :normal, state}
      _ -> {:noreply, state}
    end
  end

  def terminate(_reason, _state) do
    IO.puts "Terminate callback will sleep for 2 seconds"
    Process.sleep 2000
  end
end

Process.flag(:trap_exit, true)
MyServer.start_link
MyServer.kill
receive do
  {:EXIT, _pid, :normal} -> IO.puts "Exit signal received by parent"
end