toy/lib/toy_web/live/page_live.html.leex

<section class="phx-hero">
  <h1>It works !</h1>

  <%= if @repo_started, do: "Repo started", else: "Repo not started" %>
  <%= unless @repo_started do %><button phx-click="start_repo">Try to connect to database..</button><% end %>
</section>