Application isn't started

I am doing the code gnome course (which the application is a Hangman) and I tried to start a module with Application which uses an Agent and is complainig this:

iex(1)> Dictionary.random_word
** (exit) exited in: GenServer.call(Dictionary.Runtime.Server, {:get, &Dictionary.Impl.WordList.random_word/1}, 5000)
    ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
    (elixir 1.13.0) lib/gen_server.ex:1019: GenServer.call/3

I tried to start with the atom mod: and start_module: on the file mix.exs

def application do
    [
      # mod: { Dictionary.Runtime.Application, [] },
      start_module: { Dictionary.Runtime.Application, [] },
      extra_applications: [:logger]
    ]
  end

application.ex:

defmodule Dictionary.Runtime.Application do

  use Application

  def start(_type, _args) do
    Dictionary.Runtime.Server.start_link()
  end
end

server.ex :

defmodule Dictionary.Runtime.Server do

  @type t :: pid()

  @me __MODULE__

  alias Dictionary.Impl.WordList

  def start_link do
    Agent.start_link(&WordList.word_list/0, name: @me)
  end

  def random_word() do
    Agent.get(@me, &WordList.random_word/1)
  end
end