Copy iteration var into block-local to prevent clobbering spawned Gs.

client.go

@@ -80,7 +80,8 @@ func (client *Client) Close() error {
 	defer client.lock.Unlock()
 
 	for _, broker := range client.brokers {
-		go withRecover(func() { broker.Close() })
+		myBroker := broker // NB: block-local prevents clobbering
+		go withRecover(func() { myBroker.Close() })
 	}
 	client.brokers = nil
 	client.leaders = nil
@@ -180,7 +181,8 @@ func (client *Client) disconnectBroker(broker *Broker) {
 		delete(client.brokers, broker.ID())
 	}
 
-	go withRecover(func() { broker.Close() })
+	myBroker := broker // NB: block-local prevents clobbering
+	go withRecover(func() { myBroker.Close() })
 }
 
 func (client *Client) refreshMetadata(topics []string, retries int) error {
@@ -286,7 +288,8 @@ func (client *Client) update(data *MetadataResponse) ([]string, error) {
 			client.brokers[broker.ID()] = broker
 			Logger.Printf("Registered new broker #%d at %s", broker.ID(), broker.Addr())
 		} else if broker.Addr() != client.brokers[broker.ID()].Addr() {
-			go withRecover(func() { client.brokers[broker.ID()].Close() })
+			myBroker := client.brokers[broker.ID()] // use block-local to prevent clobbering `broker` for Gs
+			go withRecover(func() { myBroker.Close() })
 			broker.Open(client.config.ConcurrencyPerBroker)
 			client.brokers[broker.ID()] = broker
 			Logger.Printf("Replaced registered broker #%d with %s", broker.ID(), broker.Addr())