session_controller.ex

defmodule MangoWeb.Admin.SessionController do
  use MangoWeb, :controller
  plug :set_layout

  alias Mango.Administration

  def new(conn, _params) do
    conn
    |> render("new.html")
  end

  def send_link(conn, %{"session" => %{"email" => email}}) do
    user = Administration.get_admin_by_email(email)
    conn = case user do
      nil ->
       conn
       |> put_flash(:error, "Authentication error")
      user ->
       link = generate_login_link(conn, user)
       conn
       |> put_flash(:info, "You magic login link is #{link}")
      end
     conn |> render("new.html")
   end

   def create(conn, %{"token" => token}) do
     case verify_token(token) do
        {:ok, user_id} ->
          user = Administration.get_user!(user_id)
          conn
          |> assign(:current_admin, user)
          |> put_session(:admin_id, user.id)
          |> configure_session(renew: true)
          |> put_flash(:info, "Successfully logged in!")
          |> redirect(to: admin_user_path(conn, :index))
        {:error, _} ->
          conn
          |> put_flash(:error, "Authentication error")
          |> render(:new)
      end
   end

   @max_age 600 # 10 mins
   defp verify_token(token) do
     Phoenix.Token.verify(MangoWeb.Endpoint, "user", token, max_age: @max_age)
   end

  defp generate_login_link(conn, user) do
    token = Phoenix.Token.sign(MangoWeb.Endpoint, "user", user.id)
    admin_session_url(conn, :create, %{token: token})
  end

  defp set_layout(conn, _) do
    conn
    |> put_layout("admin_login.html")
  end
end

On version 1.1 of the book, line 35 is different than what is in the book.

In the Admin I section for Listing 18, it says |> redirect(to: admin_dashboard_path(conn, :index)).

For quick reference, it's on page 301 that the admin_dashboard_path typo is found.