feat: add example multi chan

__concurrent/crossbeam_n_parking_lot/examples/multi_chan.rs

@@ -0,0 +1,37 @@
+use std::thread;
+use crossbeam_channel::bounded;
+
+fn main() {
+    let (s, r) = bounded(0);
+
+    let mut ts = vec![];
+    for ti in 0..4 {
+        let copied_sender = s.clone();
+        let t = thread::spawn(move|| {
+            println!("Start: {}", ti);
+            for i in 0..100000_u64 {
+                copied_sender.send(Some(i)).unwrap();
+            }
+            println!("End: {}", ti);
+        });
+        ts.push(t);
+    }
+    let tt = thread::spawn(move || {
+        println!("Start collect");
+        let mut sum = 0_u64;
+        loop {
+            let x = r.recv().unwrap();
+            match x {
+                None => break,
+                Some(x) => sum+=x,
+            }
+        }
+        println!("Enc collect");
+        println!("Sum: {}", sum);
+    });
+    for t in ts  {
+        t.join().unwrap();
+    }
+    s.send(None).unwrap();
+    tt.join().unwrap();
+}

__concurrent/crossbeam_n_parking_lot/justfile

@@ -0,0 +1,8 @@
+_:
+  @just --list
+
+ex-multi-chan:
+  cargo r --example multi_chan
+
+
+