This is a set of projects with automatic tests, each guiding user through implementing a basic version of a particular idea, that usually is readily available as a library. DIY (Do it Yourself) in this case stands for reinventing the wheel, for learning purposes.
Routing system implementation, typically found in web application where it allows developers to hook functions (handlers) to particular paths. These functions then will be called when a particular path is accessed by users at runtime.
Slice implementation that works the same way golang slices do, with syntactical differences.