I added spaces in the domain so it can't be identified, try to concatenate the URL parts to get the link Sayed Alesawy

Great article as usual. but I have to comments: 1- in go mutex example you have to send the mutex by example in order not to create new instance with each pass which will result in no real locking, more details here: eli. thegreenplace. net/2018/beware-of-copying-mutexes-in-go/ 2- (I know this shouldn't be in the article since it is introduction :D) in redis example, the unlock function may result in a problem if one thread is stuck longer than the lock time and when back it deletes the lock, then it may have deleted another thread lock. a solution for this problem is described here: redis .io/commands/set/

thank you for the great article I liked the example of sidekiq and I will suggests that you highlight the parts of the article that you put from your experience in a different format, so it is easier for the one who already just read the chapter to find your comments which doesn't exist in the book