walk: Use a bounded queue.

Fixes #918.

src/walk.rs

@@ -9,7 +9,7 @@ use std::time::{Duration, Instant};
 use std::{borrow::Cow, io::Write};
 
 use anyhow::{anyhow, Result};
-use crossbeam_channel::{unbounded, Receiver, RecvTimeoutError, Sender};
+use crossbeam_channel::{bounded, Receiver, RecvTimeoutError, Sender};
 use ignore::overrides::OverrideBuilder;
 use ignore::{self, WalkBuilder};
 use regex::bytes::Regex;
@@ -54,7 +54,7 @@ pub fn scan(path_vec: &[PathBuf], pattern: Arc<Regex>, config: Arc<Config>) -> R
     let first_path_buf = path_iter
         .next()
         .expect("Error: Path vector can not be empty");
-    let (tx, rx) = unbounded();
+    let (tx, rx) = bounded(0x4000 * config.threads);
 
     let mut override_builder = OverrideBuilder::new(first_path_buf.as_path());