use rustls_pki_types::ServerName;
use std::sync::Arc;
use tokio::net::TcpStream;
use tokio_rustls::rustls::{ClientConfig, RootCertStore};
use tokio_rustls::TlsConnector;

// ...

let mut root_cert_store = RootCertStore::empty();
root_cert_store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
let config = ClientConfig::builder()
    .with_root_certificates(root_cert_store)
    .with_no_client_auth();
let connector = TlsConnector::from(Arc::new(config));
let dnsname = ServerName::try_from("www.rust-lang.org").unwrap();

let stream = TcpStream::connect(&addr).await?;
let mut stream = connector.connect(dnsname, stream).await?;

// ...