_______ is a mechanism used in Go's HTTP server to provide additional functionalities such as logging, authentication, or request modification.

The correct answer is Middleware. Middleware is a mechanism commonly used in Go's HTTP server to provide additional functionalities such as logging, authentication, request modification, rate limiting, and more. Middleware functions sit between the incoming request and the handler, allowing you to intercept and process the request before it reaches the main handler. Middleware provides a modular way to add cross-cutting concerns to your HTTP server, enhancing its capabilities and maintainability. It is widely used in Go web development to streamline common tasks and improve code organization.