Using the glob pattern in the routing component breaks the YamlFileLoader:

e.g. given following config with routing.yml files in the directory

domain:
    resource: '../src/Project/**/Infrastructure/Resources/Routing/routing.yml'
    prefix: /

results that https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Routing/Loader/YamlFileLoader.php#L148 receives an array of RouteCollection and not a single RouteCollection, which results in a fatal error:

  [Symfony\Component\Debug\Exception\FatalThrowableError]  
  Call to a member function addPrefix() on array