sudo nano /etc/apt/sources.list
replace
deb http://us.archive.ubuntu.com/ubuntu/ xenial main restricted
with
deb mirror://mirrors.ubuntu.com/mirrors.txt xenial main restricted
Manual apt mirror selection
wget -qO - mirrors.ubuntu.com/mirrors.txt
References
https://linuxconfig.org/how-to-select-the-fastest-apt-mirror-on-ubuntu-linux