Middleware chaining

The Echo framework provides three mechanisms for inserting middleware into your request-processing pipeline. The Echo instance's Use(MiddlewareFunc) helper method is the most common way to add normal post-routing middleware. As you may recall, for flexibility we showed you how to use the Group(string) Echo method to organize routes. The Use(MiddlewareFunc) helper method is also available on Group instances so that you can apply middleware functions only to particular groupings of routes as well. Use tells the Echo instance, or grouping instance, that we wish to insert the middleware specified as a parameter into our middleware chain. It should be made clear that the order of your Use calls is very important. The order of the middleware insertion stipulates the order in which the middleware chain will be performed. For example, you might want two middleware...