diff --git a/src/main.rs b/src/main.rs
index 8ca40a7..8cb8f16 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+//! https://www.zupzup.org/epoll-with-rust/index.html
+
 use std::collections::HashMap;
 use std::io::{self, prelude::*};
 use std::net::{TcpListener, TcpStream};