use rand::distributions::Alphanumeric;
use rand::{thread_rng, Rng};
use std::iter::repeat_with;
#[allow(dead_code)]
fn random_str(n: usize) -> String {
let mut rng = thread_rng();
repeat_with(|| rng.sample(Alphanumeric) as char)
.take(n)
.collect()
}