update views+1 doesn't work

I need to update counter views:

In Controller:

PHP Code:

public function show(string $slug)
  $post = $this->findPost($slug);
  if ($post) {
    $this->postModel->set('views', 'views+1')->where('id', $post->id)->update();
    return view('blog/post', $data);
  }
} 


In Modal:

PHP Code:

class PostModel extends Model
{
    protected $table = 'posts';
    protected $allowedFields = [
        'id',
        'title',
        'lang_id',
        'slug',
        'summary',
        'content',
        'meta_title',
        'meta_keywords',
        'meta_description',
        'reference',
        'reference_link',
        'image',
        'image_caption',
        'image_external_url',
        'post_type',
        'author_id',
        'status',
        'published',
        'visibility',
        'is_slider',
        'is_featured',
        'is_breaking',
        'comments',
        'views',
        'created_by'];
    protected $returnType = 'object';
    protected $primaryKey = 'id';
    protected $useSoftDeletes = true;
    protected $useTimestamps = true;
} 


In action views table didn't update and show always 0.

How do can I fix this problem?