Drupal 8 - Load taxonomy terms sorted by weight

module.install

/**
 * Get taxonomy terms sorted by weight.
 *
 * @param int $vid
 *   The vocabulary id.
 *
 * @return array
 *   Returns an array of term id | name.
 *
 * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
 * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
 */
private function getTaxonomyTermsSortedByWeight($vid) {

  // Initialize the items.
  $items = [];

  // Get the term storage.
  $entity_storage = $this->entityTypeManager->getStorage('taxonomy_term');

  // Query the terms sorted by weight.
  $query_result = $entity_storage->getQuery()
    ->condition('vid', $vid)
    ->sort('weight', 'ASC')
    ->execute();

  // Load the terms.
  $terms = $entity_storage->loadMultiple($query_result);

  foreach ($terms as $term) {
    $items[$term->id()] = $term->getName();
  }

  // Return the items.
  return $items;
}