Use metadata.len() istead of metadata.size() for other platforms

Signed-off-by: hr567 <hr567@hr567.me>

src/main.rs

@@ -2,7 +2,6 @@ use std::cell::RefCell;
 use std::collections::{BTreeMap, HashMap, VecDeque};
 use std::fmt::Write;
 use std::io;
-use std::os::unix::prelude::*;
 use std::path::PathBuf;
 use std::rc::{Rc, Weak};
 use std::sync::{
@@ -61,7 +60,7 @@ async fn main() -> io::Result<()> {
             let metadata = entry.metadata().await?;
             let task = Task {
                 file: entry.path(),
-                size: metadata.size() as usize,
+                size: metadata.len() as usize,
             };
             res.push(task);
         }