Function crypto_crawler::crawl_l2_event

pub fn crawl_l2_event(
    exchange: &str, 
    market_type: MarketType, 
    symbols: Option<&[String]>, 
    on_msg: Arc<Mutex<dyn FnMut(Message) + Send + 'static>>, 
    duration: Option<u64>
)

Crawl level2 orderbook update events.