Error: could not lookup MyApp.Repo because it was not started or it does not exist

Hello,

I want to start a module (MyApp.MyAgent) using Agent that will fetch some data from DB (and thus use MyApp.Repo) and keep it in memory, and I want the data to be available when the application starts. So I add it as a child to the superviser but the compiler complains that MyApp.Repo has not yet been started when aliasing it in MyApp.MyAgent:

def start(_type, _args) do
  # List all child processes to be supervised
  children = [
    # Start the Ecto repository
    MyApp.Repo,
    # Start the endpoint when the application starts
    MyAppWeb.Endpoint,
    # Starts a worker by calling: MyApp.Worker.start_link(arg)
    # {MyApp.Worker, arg},
    MyApp.MyAgent.start_link()
  ]

defmodule MyApp.MyAgent do
  import Ecto.Query, warn: false
  alias MyApp.Repo
  alias MyApp.SomeContext.SomeSchema

  def start_link do
    ids = Repo.all(from s in SomeSchema, select: s.id)

    Agent.start_link(fn -> ids end, name: __MODULE__)
  end

  def all do
    Agent.get(__MODULE__, & &1)
  end
end

Thank you for any help!