Responding with :stop allows call of `terminate`

A GenServer in Elixir has two lifecycle methods, init and terminate. init is called when the GenServer is started with GenServer.start_link.

What I learned today is that there is a terminate method in case there's any resources that need to be cleaned up when the GenServer is shut down. The terminate method is called when the :stop message is returned from either handle_cast or handle_call:

defmodule Cache do
  use GenServer
  
  #... a lot of other code

  def handle_cast({:something, 1}, state) do
    IO.puts "This executes first"
    {:stop, "This is my reason for stopping", state}
  end

  def terminate(reason, state)
    IO.puts "Then this executes"
  end
end