regex loglines with rust

log_regex.rs

use regex::Regex;

fn main() {
    let datetime = r"[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1]) (2[0-3]|[01][0-9]):[0-5][0-9]:[0-5][0-9],[0-9][0-9][0-9]";
    let host = r"([^\s]+)";
    let service = r"([^\s]+)";
    let message = r"(.*)";

    let re = Regex::new(&format!("(?P<datetime>({d})) (?P<hostname>({h}))] (?P<service>({s})) (?P<message>({m}))",
                                 d = datetime, h = host, s = service, m = message)).unwrap();

    let log_line = "[2006-02-08 22:20:02,165 192.168.0.1] fbloggs  Protocol problem: connection reset";

    let date = re.captures(log_line).unwrap();
    println!("{:?}", &date)
}