This is definitely a bug.Laravel offers predefined code in routes/api.php
Route::middleware('auth:api')->get('/user', function (Request $request) {
return $request->user();
});
which is unabled to be processed by:
php artisan route:cache
This definitely should be fixed by Laravel team.(check the link),
simply if you want to fix it you should replace routes\api.php code with some thing like :
Route::middleware('auth:api')->get('/user', 'UserController@AuthRouteAPI');
and in UserController put this method:
public function AuthRouteAPI(Request $request){
return $request->user();
}