Provides functions to attach random user-agent generation to a Collector via OnRequest. Implements realistic desktop and mobile user agent strings for multiple browsers (Firefox, Chrome, Edge, Opera) and devices (Pixel, Nexus). Demonstrates the extension pattern (function that takes a Collector and modifies its callbacks) and is reusable in any scraping project requiring user-agent rotation.

Implements a configurable request queue with a Storage interface, allowing multiple consumer goroutines to process requests concurrently. The InMemoryQueueStorage is the default backend, but custom storage backends (e.g., Redis, disk) can be plugged in by implementing the Storage interface. This decouples queue management from the scraping logic and is a clean, reusable pattern for rate-limited or distributed scraping.

Provides a RoundRobinProxySwitcher function that returns a ProxyFunc, rotating through a list of proxy URLs for each request. The implementation stores the proxy URL in the request context for later retrieval. This is a reusable component that can be used with any Go HTTP client or scraper needing proxy rotation.

Defines the Storage interface for persisting visited URLs and cookies, with an InMemoryStorage implementation. The interface is minimal and clean, allowing easy substitution with persistent backends (e.g., database, file). The StringifyCookies/UnstringifyCookies helpers are also reusable for cookie serialization.