get_user_by_email! returns a %LibraryApi.Library.User{} not {:ok, %LibraryApi.Library.User{}}, so your case in your controller doesn’t match.

Also, you probably know this, but never store user passwords in the database unhashed.

I’m not a JWT power user or anything but can’t you just do

  def render("token.json", %{user: user}) do
    data = %{id: user.id, email: user.email, username: user.username}
    jwt = %{data: data, sub: user.id}
    token = MyAppWeb.Token.generate_and_sign!(jwt)
    %{token: token}
  end

No need to do this, just update here with more information and we’ll be able to provide a more detailed answer.