Wireguard on Ubuntu 18.04.4 (LTS)?

[wireguard]

Hello all,
I just tried to set up a new (virtual) machine with Ubuntu 18.04.4 (LTS) and 
wireguard, but apt install wireguard reports “E: Unable to locate package 
wireguard”. This is not really what I expect after looking at 
https://www.wireguard.com/install/. 
Any idea?
Thanks, Joachim