Ah.. It was my huge mistake, but of course I bought it thinking it would be a lecture, but I was tempted by the word nestjs and ended up buying it.. Since there is only one Korean textbook for nestjs on the market, it might be good to look at it as a PDF. If I go back, I think I will do better and buy it for reference.. I think it will be very helpful since I don't have many opportunities to study docker or swagger. In class-validator, you can see isIn, match, and more, so it will be helpful as a reference.