Wa alaikum salaam
All perfect praise be to Allah
وَقَالُوا إِنْ هِيَ إِلَّا حَيَاتُنَا الدُّنْيَا وَمَا نَحْنُ
And they say, "There is none but our worldly life, and we will not be
( Surah al an'aam verse 29.)
Allahu a'lam it's like youre rejecting the verses from the Quran completely by saying yolo. So, to be on safe side avoid this as much as possible even though you don't mean it.
I read somewhere:
The non muslims say YOLO
So, Do all the misdeeds this dunya has to offer.
The muslim says YOLO(in this world)
So, Make salaah go on hajj and prove you believe.
So, it all depends on what you mean by it. If you don't mean to say that there is no life hereafter than you are not doing any kufr. Now, by your question and your use. I will still advice you to avoid it and be on safe side.
Though i am not a mufti so i cannot declare but i suspect it to be makrooh.
Al-Bukhaari and Muslim narrated from Abu Hurayrah that the Messenger
of Allah (blessings and peace of Allah be upon him) said: “ A person
may speak a word, not realizing what he is saying, and he will fall
because of it into the Fire further than the distance between the East
Allah says (interpretation of the meaning):
“Not a word does he (or she) utter but there is a watcher by him ready
(to record it)” [50:18]
Allah knows Best