settings.docker.php.twig

<?php

$settings['trusted_host_patterns'] = array(
  '^{{ projectname }}\.docker\.localhost$',
);
$databases = array (
  'default' => array (
    'default' => array (
      'driver' => 'mysql',
      'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
      'database' => 'drupal',
      'username' => 'drupal',
      'password' => 'drupal',
      'host' => 'mariadb',
      'port' => '3306',
      'prefix' => '',
    ),
  ),
);