How to build image with delve?

I am trying to follow the documentation on building the images, with debugging enabled using the command make DEBUG=1 docker. The build works and I am able to run istio no problem. But I do not understand how to actually go through remote debugging. I tried to exec into the container but dlv does not seem to be installed. Am I missing something? I followed up to the point of debug uses the istionightly/base_debug for its base image though not sure what this provides.

I assumed debug enabled something similar to this https://medium.com/@linsun_unc/debug-istio-components-with-goland-b0f9f9f60384, which I also tried to follow with no luck.

I am trying to enable debug istio 1.1.0