sub timed {
  my $cb = pop;
  my ($self, $url) = @_;
  my $is_done;

  my $done = sub {
    return if $is_done;
    $is_done = 1;
    $cb->(@_);
  };

  Mojo::IOLoop->timer($self->timeout, sub { $done->(Mojo::Transaction::HTTP->new) });
  $self->ua->get($url, $done);
}