valid fqdn regex

fn is_fqdn(hostname: &str) -> bool {
  let re: Regex = Regex::new("^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9])\\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\\-]*[A-Za-z0-9])$").unwrap();
  re.is_match(hostname)
}

is_fqdn("google.com")