How to get awaitable Thread.Sleep?
The other answers suggesting starting a new thread are a bad idea - there's no need to do that at all. Part of the point of async/await is to reduce the number of threads your application needs.
You should instead use Task.Delay which doesn't require a new thread, and was designed precisely for this purpose:
// Execution of the async method will continue one second later, but without
// blocking.
await Task.Delay(1000);