Swift 3 dispatch_async or dispatch_sync (dispatch_get_main_queue()) dont work.

Question

I have working code on Swift2.2 with dispatch_async and dispatch_sync under below.

 dispatch_async(dispatch_get_main_queue()){

   // Working Swift2.2

  }

But when i use it on Swift 3 gives me;

'dispatch_async' has been replaced by instance method 'DispatchQueue.asynchronously(execute:)'

That error I need your ideas Thank you !