HAProxy stands for High Availability Proxy, If you are running the Ubuntu Xenial-16.04 LTS operating system and install HAProxy-1.6-stable version

execute the below commands to install HAProxy-1.6-stable

# apt-get update

# apt-get install haproxy -t trusty-backports

You will get HAProxy 1.6-stable version, which means you may not  latest one.

First, need to enable a Dedicated PPA using below commands on Ubuntu Xenial-16.04 LTS

# apt-get install software-properties-common

# add-apt-repository ppa:vbernat/haproxy-1.6

Execute the below commands,

# apt-get update

# apt-get install haproxy

Now, able to access the  latest release of HAProxy-1.6-stable