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: testonly.rs
    path of file: ./repos/nearcore/chain/network/src/stun
    
    the code of the file until where you have to start completion: use std::sync::Arc;

struct TestAuthHandler;

impl turn::auth::AuthHandler for TestAuthHandler {
    fn auth_handle(
        &self,
        _username: &str,
        _realm: &str,
        _src_addr: std::net::SocketAddr,
    ) -> Result<Vec<u8>, turn::Error> {
        unimplemented!();
    }
}

/// STUN server. Use new() to spawn a new server, use close() to close it.
/// Remember to call close() explicitly, otherwise the server will keep running
/// in the background.
pub(crate) struct Server {
    inner: turn::server::Server,
    addr: std::net::SocketAddr,
}

impl Server {
    /// Spawns a new STUN 
    
    pub async fn new() -> Self {
        let server_conn = Arc::new(tokio::net::UdpSocket::bind("[::1]:0").await.unwrap());
        let server_addr = server_conn.local_addr().unwrap();

        Self {
            addr: server_addr,
            inner: turn::server::Server::new(turn::server::config::ServerConfig {
                conn_configs: vec![turn::server::config::ConnConfig {
                    conn: server_conn,
                    relay_addr_generator: Box::new(
                        turn::relay::relay_none::RelayAddressGeneratorNone {
                            address: "[::]".to_owned(),
                            net: Arc::new(webrtc_util::vnet::net::Net::new(None)),
                        },
                    ),
                }],
                realm: String::default(),
                auth_handler: Arc::new(TestAuthHandler),
                channel_bind_timeout: std::time::Duration::from_secs(0),
            })
            .await
            .unwrap(),
        }
    }