Error message

Deprecated function: Array and string offset access syntax with curly braces is deprecated in include() (line 571 of vendor/composer/ClassLoader.php).

include() (Line: 571)
Composer\Autoload\includeFile('/home/OmanPost/public_html/modules/omanpost/src/Controller/OmanPostController.php') (Line: 428)
Composer\Autoload\ClassLoader->loadClass('Drupal\omanpost\Controller\OmanPostController')
spl_autoload_call('Drupal\omanpost\Controller\OmanPostController')
class_exists('\Drupal\omanpost\Controller\OmanPostController') (Line: 23)
Drupal\Core\DependencyInjection\ClassResolver->getInstanceFromDefinition('\Drupal\omanpost\Controller\OmanPostController') (Line: 117)
Drupal\Core\Controller\ControllerResolver->createController('\Drupal\omanpost\Controller\OmanPostController::epost_subscriber') (Line: 69)
Drupal\Core\Controller\ControllerResolver->getControllerFromDefinition('\Drupal\omanpost\Controller\OmanPostController::epost_subscriber', '/epost-subscriber') (Line: 85)
Drupal\Core\Controller\ControllerResolver->getController(Object) (Line: 141)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 80)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 191)
Drupal\page_cache\StackMiddleware\PageCache->fetch(Object, 1, 1) (Line: 128)
Drupal\page_cache\StackMiddleware\PageCache->lookup(Object, 1, 1) (Line: 82)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 49)
Asm89\Stack\Cors->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 708)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)