Create virtual network interface in Ubuntu 16.04

As has been mentioned in multiple answers on this site before, wlan:0 is not a "virtual interface" - it's the old way for ifconfig of assigning multiple IP addresses. With more modern tools like ip, you just assign multiple IP addresses with ip addr add .. to the same interface. It will also list all address from ifconfig's wlan:0, wlan:1 etc. under wlan, because that's how modern Linux kernels store them internally.

Note that working with multiple IP addresses can be a PITA, because you have to make sure all your applications bind to the correct address. Not all applications are able to do this. You didn't say what the tool you are trying to use is, and how it wants to make use of those addresses.

There are multiple other ways to create real virtual network interfaces, in case your tool really needs multiple interfaces, and not just multiple IP addresses. Which way to use depends on what the tool needs.