simple_task.ex

defmodule App.UserService do

  def create_user(params) do
    %App.User{}
    |> App.User.changeset(params)
    |> App.Repo.insert()
    |> case do
      {:ok, user} ->
        Task.start(fn -> send_email_to_user(user) end) # 🎉
        {:ok, user}

      {:error, changeset} ->
        {:error, changeset}
    end
  end
  
  defp send_email_to_user(user) do
    # send the email
  end
end