Mark's point was that you can create an arbitrary wrapper type around another interface, so that the behaviors are composed. This is the most flexible way to do things. If there's already a wrapper type that does what you want, however, then you can simply use that. They are both examples of composition, and both "the Go-ic way to do it."

Composition is often overlooked by people who are fixated on other ways of doing things, like inheritance or generics. But in many ways, it's cleaner, since composition allows you to link together many modules without peeking inside.

It's funny that people have accepted the reality of dynamic languages, but can't seem to "get" the idea of statically typed language without generics. There isn't a troll comment in every Python article that it would be better with static typing. Type systems are a little bit like body armor-- development can be slower, but in exchanged you get a little more confidence in the program. People have accepted the idea of going naked, and the idea of medieval-style full plate armor, but the idea that you might want some type safety, but not go overboard often seems to fall on deaf ears.