First you teach them how to write idiomatic code (non-performant), and then you teach them how to make the idiomatic code more performant. It's very common for

First you teach them how to write idiomatic code (non-performant), and then you teach them how to make the idiomatic code more performant. It's very common for new users (in any language, not just Go) to try to jump right to the end, but focusing on performance before understanding basic language building blocks is a recipe for frustration, both for the new users and for the language designers.