You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: custom_provider.rs
    path of file: ./repos/hickory-dns/crates/resolver/examples
    
    the code of the file until where you have to start completion: #![recursion_limit = "128"]

#[cfg(any(feature = "webpki-roots", feature = "native-certs"))]
use {
    hickory_resolver::config::{ResolverConfig, ResolverOpts},
    hickory_resolver::name_server::{ConnectionProvider, GenericConnector, RuntimeProvider},
    hickory_resolver::proto::iocompat::AsyncIoTokioAsStd,
    hickory_resolver::pro
    
async fn lookup_test<R: ConnectionProvider>(resolver: AsyncResolver<R>) {
    let response = resolver.lookup_ip("www.example.com.").await.unwrap();

    // There can be many addresses associated with the name,
    //  this can return IPv4 and/or IPv6 addresses
    let address = response.iter().next().expect("no addresses returned!");
    if address.is_ipv4() {
        assert_eq!(address, IpAddr::V4(Ipv4Addr::new(93, 184, 216, 34)));
    } else {
        assert_eq!(
            address,
            IpAddr::V6(Ipv6Addr::new(
                0x2606, 0x2800, 0x220, 0x1, 0x248, 0x1893, 0x25c8, 0x1946
            ))
        );
    }
}