use walkdir::WalkDir;

for entry in WalkDir::new("foo").min_depth(1).max_depth(3) {
    println!("{}", entry?.path().display());
}

use walkdir::{DirEntry, WalkDir};

fn is_hidden(entry: &DirEntry) -> bool {
    entry.file_name()
         .to_str()
         .map(|s| s.starts_with("."))
         .unwrap_or(false)
}

for entry in WalkDir::new("foo")
                     .into_iter()
                     .filter_entry(|e| !is_hidden(e)) {
    println!("{}", entry?.path().display());
}