diff --git a/core/port.go b/core/port.go
index 9376f70..09870de 100644
--- a/core/port.go
+++ b/core/port.go
@@ -4,6 +4,7 @@ package core
 
 import (
 	"bufio"
+	"io"
 	"net"
 	"sync"
 	"time"