Drupal

  // Legacy procedural code.
  function hook_do_stuff() {
    $lock = lock()->acquire('stuff_lock');
    // ...
  }

  // Correct procedural code.
  function hook_do_stuff() {
    $lock = \Drupal::lock()->acquire('stuff_lock');
    // ...
  }

  // The preferred way: dependency injected code.
  function hook_do_stuff() {
    // Move the actual implementation to a class and instantiate it.
    $instance = new StuffDoingClass(\Drupal::lock());
    $instance->doStuff();

    // Or, even better, rely on the service container to avoid hard coding a
    // specific interface implementation, so that the actual logic can be
    // swapped. This might not always make sense, but in general it is a good
    // practice.
    \Drupal::service('stuff.doing')->doStuff();
  }

  interface StuffDoingInterface {
    public function doStuff();
  }

  class StuffDoingClass implements StuffDoingInterface {
    protected $lockBackend;

    public function __construct(LockBackendInterface $lock_backend) {
      $this->lockBackend = $lock_backend;
    }

    public function doStuff() {
      $lock = $this->lockBackend->acquire('stuff_lock');
      // ...
    }
  }