Use defer to close the channel in case of error

physical/etcd.go

@@ -355,9 +355,10 @@ func (c *EtcdLock) Lock(stopCh <-chan struct{}) (<-chan struct{}, error) {
 	// Get the local lock before interacting with etcd.
 	c.lock.Lock()
 	defer c.lock.Unlock()
+	var err error
 
 	// Check if the lock is already held.
-	if err := c.assertNotHeld(); err != nil {
+	if err = c.assertNotHeld(); err != nil {
 		return nil, err
 	}
 
@@ -384,14 +385,20 @@ func (c *EtcdLock) Lock(stopCh <-chan struct{}) (<-chan struct{}, error) {
 
 	// Create a channel to signal when we lose the semaphore key.
 	done := make(chan struct{})
+	defer func(err *error) {
+		if *err != nil {
+			close(done)
+		}
+	}(&err)
+
 	go c.periodicallyRenewSemaphoreKey(done)
 
 	// Loop until the we current semaphore key matches ours.
 	for semaphoreKey != currentSemaphoreKey {
-		var err error
+		var response *etcd.Response
 
 		// Start a watch of the entire lock directory, providing the stop channel.
-		response, err := c.client.Watch(c.semaphoreDirKey, currentEtcdIndex+1, true, nil, boolStopCh)
+		response, err = c.client.Watch(c.semaphoreDirKey, currentEtcdIndex+1, true, nil, boolStopCh)
 		if err != nil {
 
 			// If the error is not an etcd error, we can assume it's a notification
@@ -401,7 +408,6 @@ func (c *EtcdLock) Lock(stopCh <-chan struct{}) (<-chan struct{}, error) {
 			if _, ok := err.(*etcd.EtcdError); !ok {
 				_, err = c.client.Delete(c.semaphoreKey, false)
 			}
-			close(done)
 			return nil, err
 		}
 
@@ -409,14 +415,13 @@ func (c *EtcdLock) Lock(stopCh <-chan struct{}) (<-chan struct{}, error) {
 		// this is an error and nothing else needs to be done.
 		if response.Node.Key == semaphoreKey &&
 			(response.Action == "delete" || response.Action == "expire") {
-			close(done)
-			return nil, EtcdSemaphoreKeyRemovedError
+			err = EtcdSemaphoreKeyRemovedError
+			return nil, err
 		}
 
 		// Get the current semaphore key and etcd index.
 		currentSemaphoreKey, _, currentEtcdIndex, err = c.getSemaphoreKey()
 		if err != nil {
-			close(done)
 			return nil, err
 		}
 	}