Basic supervision tree with Elixir (example provided by @Quarkex).

application.ex

defmodule Client.Application do
  @moduledoc false
  
  use Application
  
  @impl true
  def start(_type, _args) do
    children = [
      {Client, []}
    ]
    
    opts = [strategy: :one_for_one, name: Client.Supervisor]
    
    Supervisor.start_link(children, opts)
  end
end

client.ex

defmodule Client do
  @moduledoc false
  use GenServer
  
  def start_link(opts \\ %{}),
    do: GenServer.start_link(__MODULE__, opts)
    
  def init(state) do
    schedule_work(state[:interval] || 1)
    {:ok, state}
  end
  
  def handle_info(:work, state) do
    perform_work()
    schedule_work(state[:interval] || 1)
    {:noreply, state}
  end
  
  defp schedule_work(interval),
    do: Process.send_after(self(), :work, interval * 1000)
    
  def perform_work() do
    # Do some work!
  end
end