use Mojo::Base 'Mojolicious';
# This method will run once at server start
sub startup {
  my $self = $_[0];
  $self->app->config(
     hypnotoad => {
      listen => ['http://'.$SERVER_ADDRESS.':'.$SERVER_PORT]
      }
  );
  my $DOCUMENT_ROOT = '...';
  $self->helper(document_root => sub { $DOCUMENT_ROOT });
  # I also add a logger object
  my $logger = Mojo::Log->new;
  $self->helper(applog => sub { $logger });
  ...
}