Sometimes, there are use cases where the same application logic needs to be applied to a multitude of resources within an application. A prime example of this type of logic is protecting resources behind an authentication mechanism. Some resources such as the login or static resources typically do not need this authentication logic, but other resources such as our reminder creation, snoozing, need to be protected by authentication. We can accomplish this feat with the use of middleware.

A middleware can be thought of as a wrapper for the handlers we create. An Echo middleware is defined as a function that takes the next function to call as a parameter, and returns an Echo handler. By having the parameter be the next handler function to call, we are able to build a chain of handlers: