You need too call Supervisor.stop from another process to stop the supervisor in a clean way. Now, what are you trying to do exactly?

Here’s what I came up with:

defmodule RunForAWhileThenStop do

  use GenServer
  def start_link(state) do
    GenServer.start_link(__MODULE__, state, name: __MODULE__)
  end

  @impl true
  def init(opts) do
    time = Keyword.get(opts, :time, 60_000)
    children = [ ... ]

    Process.send_after(self(), :stop, time)
    Supervisor.start_link(children, strategy: :one_for_one)
  end

  @impl true
  def handle_info(:stop, state) do
    {:stop, :normal, state}
  end

This way I can something like RunForAWhileThenStop.start_link(time: 30_000) and let my GenServer run for 30 seconds and then stop.

You should have a look at GenServer timeout.

It allows You to stop the server after a certain inactivity period.

Also doing this on a supervisor will kill all children, unless they trap exit.