remove unused code

common/signal/notifier.go

@@ -1,7 +1,5 @@
 package signal
 
-import "io"
-
 // Notifier is a utility for notifying changes. The change producer may notify changes multiple time, and the consumer may get notified asynchronously.
 type Notifier struct {
 	c chan struct{}
@@ -26,18 +24,3 @@ func (n *Notifier) Signal() {
 func (n *Notifier) Wait() <-chan struct{} {
 	return n.c
 }
-
-type nCloser struct {
-	n *Notifier
-}
-
-func (c *nCloser) Close() error {
-	c.n.Signal()
-	return nil
-}
-
-func NotifyClose(n *Notifier) io.Closer {
-	return &nCloser{
-		n: n,
-	}
-}