Varnish 4.1 install on Ubuntu

apt install -y apt-transport-https
curl https://repo.varnish-cache.org/GPG-key.txt | apt-key add -
echo "deb https://repo.varnish-cache.org/ubuntu/ trusty varnish-4.1" >> /etc/apt/sources.list.d/varnish-cache.list
apt update && apt -y upgrade
apt -y install varnish