net: add import comments.

Change-Id: Ifab0fdaec1d810d268b7c19ad30f476802203b37
diff --git a/netutil/listen.go b/netutil/listen.go
index a2591f8..b317ba2 100644
--- a/netutil/listen.go
+++ b/netutil/listen.go
@@ -4,7 +4,7 @@
 
 // Package netutil provides network utility functions, complementing the more
 // common ones in the net package.
-package netutil
+package netutil // import "golang.org/x/net/netutil"
 
 import (
 	"net"