OnLoadExample.ex

defmodule SomeProtocol do
  @on_load :start_agent

  def start_actor() do
    {result, pid} = Agent.start_link(fn -> 0 end)
    result
  end 
  
  def __using__() do
    quote do
      @on_load :add_me
      def add_me() do
        Agent.update fn modules -> [__MODULE__ | modules] end
      end
    end
  end 

end