defmodule SomeModule do
  def do_something(token) do
    # Guardian.Token.Jwt is a library module in the guardian library
    # MyApp.Guardian is a module defined inside my application
    Guardian.Token.Jwt.decode_token(MyApp.Guardian, token)
  end

  def do_something_else do
    Application.get_env(:my_app, MyApp.Guardian)
  end
end

defmodule SomeModule do
  alias MyApp.Guardian

  def do_something(token) do
    # elixir now can't find the Guardian.Token.Jwt module because it is
    # looking for MyApp.Guardian.Token.Jwt which is not a real module
    Guardian.Token.Jwt.decode_token(Guardian, token)
  end

  def do_something_else do
    Application.get_env(:my_app, Guardian)
  end
end