async fn check_for_valid_shard_service(&self) {
        let group_num = self.config.lock().unwrap().groups.len();
        if group_num == 0 {
            self.update_config().await;
        }
    }
/// Since there is no group when startup,
/// client request has to wait until there is valid config.
Since there is no group when startup,
client request has to wait until there is valid config.
Since there is no group when startup client request has to wait until there is valid config .
async fn check_for_valid_shard_service(&self) {
        let group_num = self.config.lock().unwrap().groups.len();
        if group_num == 0 {
            self.update_config().await;
        }
    }
async fn check_for_valid_shard_service ( & self ) { let group_num = self . config . lock ( ) . unwrap ( ) . groups . len ( ) ; if group_num == 0 { self . update_config ( ) . await ; } }
Since there is no group when startup,
client request has to wait until there is valid config.
Since there is no group when startup client request has to wait until there is valid config .
&self
&self