Middleware

Middleware functions are a common concept in modern web development. A middleware function is one that has access to both the request and response objects in an application and can run the subsequent middleware after it is processed.

Middleware creation and registration in Koa is straightforward and is one of the reasons the framework is so widely adopted.

Cascading in Koa

Koa takes advantage of async functions to make middleware functions run in a truly cascaded fashion. The registered middlewares run in a stack-like manner and run from one level to the other until there is no other middleware to run.

The use of async functions is an improvement over other frameworks that have tried to implement stack-like middleware...