lib/supervisor.ex

defmodule Exsftpd.Supervisor do
  use Supervisor

  def start_link do
    Supervisor.start_link(__MODULE__, :ok)
  end

  def init(:ok) do
    options = Application.get_env(:exsftpd, Exsftpd.Server)

    children = [
      {Exsftpd.Server, options}
    ]

    Supervisor.init(children, strategy: :one_for_one)
  end
end