Illuminate\Contracts\Container\BindingResolutionException Target class [Api\BookController] does not exist. http://127.0.0.1:8000/api/books code example

Example: Illuminate\Contracts\Container\BindingResolutionException Target class [SlugController] does not exist.

Route::get('/test/{slug}',  'App\Http\Controllers\SlugController@show' );