The recently released Ubuntu 18.04.3 includes Linux Kernel 5.0 among several new features and improvements but you won’t get it by default. This tutorial demonstrates how to get Linux Kernel 5 in Ubuntu 18.04 LTS.
Text version of this topic is here: https://itsfoss.com/ubuntu-hwe-kernel/
The idea is to install HWE kernel.
For desktop:
sudo apt install --install-recommends linux-generic-hwe-18.04 xserver-xorg-hwe-18.04
For servers:
sudo apt-get install --install-recommends linux-generic-hwe-18.04
Do note that HWE is enabled for people who downloaded and installed Ubuntu 18.04.2. So these users will get Kernel 5.0 without any trouble.