the download some question

[xiangyuan]

we have a downloader code just like the follow:
`
let result = Downloader::new(url, &mut file).threads(4).callback(Box::new(|pro, total, speed| {

println!("---->>progress {:.2}% --- total {:?} --speed {}", (pro as f64 / (total as f64)) * 100.0, format_size(total, BINARY), speed);

}), 50).cache_path(PathBuf::from("./")).threshold_memory(5 * 1024 * 1024).download().map_err(|e| {

println!("{:?}", e);

});
`
my question is, do I have some way just post event in the callback function?