diff --git a/synchronization/read_write_lock.md b/synchronization/read_write_lock.md
index 644d383..5ca9eca 100644
--- a/synchronization/read_write_lock.md
+++ b/synchronization/read_write_lock.md
@@ -8,6 +8,7 @@ package router
 
 import (
 	"sync"
+	"net"
 )
 
 type Socket  string
@@ -108,4 +109,4 @@ go func(r *Router){
 	// until counter = 0 Write can be acquired
 }(router)
 
-```
\ No newline at end of file
+```