defmodule Sandbox do
   use GenServer

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

  @impl true

  def init(_) do
    :observer.start
    main()
    {:ok, :running}
  end

  def main do
    IO.puts("Hello World!")
  end

This is part of the application Foo. Sandbox is a supervised GenServer which executes the main function when Foo is started and whenever Sandbox crashes and is restarted by the Supervisor. :observer displays it as Elixir.Sandbox under its Applications tab.

However, if main is changed as follows-

  def main do
    IO.puts("Hello World!")
    main()
  end

:observer no longer shows the app nor the Elixir.Sandbox GenServer process which seems to indicate that either the Supervisor or the GenServer didn’t start. (Please correct me if this is not actually the case.)

The goal: To keep mainrunning perpetually even after its restarted by the Supervisor. What’s the best way to accomplish this?

Edit: use GenServer added