macos: add screenlock example (#202)

Author: progrium

macos/_examples/screenlock/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"log"
+
+	"github.com/progrium/macdriver/macos"
+	"github.com/progrium/macdriver/macos/appkit"
+	"github.com/progrium/macdriver/macos/foundation"
+)
+
+func main() {
+	macos.RunApp(func(app appkit.Application, delegate *appkit.ApplicationDelegate) {
+		dnc := foundation.DistributedNotificationCenter_NotificationCenterForType(foundation.LocalNotificationCenterType)
+		dnc.AddObserverForNameObjectQueueUsingBlock("com.apple.screenIsLocked", nil, foundation.OperationQueue_MainQueue(), func(notification foundation.Notification) {
+			log.Println("screen is locked")
+		})
+		dnc.AddObserverForNameObjectQueueUsingBlock("com.apple.screenIsUnlocked", nil, foundation.OperationQueue_MainQueue(), func(notification foundation.Notification) {
+			log.Println("screen is unlocked")
+		})
+	})
+}