io_uring based close() instead standard one

[lukaszml]

Currently client handling methods uses the standard 'close' function to close the connection after sending data. Due to the fact that in HTTP protocol, closing a connection is a common as accepting, it might be a good to implement 'close' using io_uring. https://unixism.net/loti/ref-liburing/submission.html#c.io_uring_prep_close

[GeorgiyX]

Thanks, I'll fix it