// add an extra middleware with below handler
public function handle($request, Closure $next)
{ if(!in_array($request->headers->get('accept'), ['application/json', 'Application/Json'])) return response()->json(['message' => 'Unauthenticated.'], 401); return $next($request);
}
//set priority in app/Http/Kernel.php

You're trying to redirect to a named route whose name is login, but you have
no routes with that name:
Route::post('login', [ 'as' => 'login', 'uses' => 'LoginController@do']);
The 'as' portion of the second parameter defines the name of the route. The
first string parameter defines its route.