Asynchronous BlueprintCallable

What I’m asking is how should this be declared in the blueprint library

If I just declare:

UFUNCTION(BlueprintCallable, Category = "Online.Hello.hello")
static void SendHello(FString Message);

The control output of the block created will be activated immediately.

How do I declare this in a way that Unreal knows that this is asynchronous?

I’d guess it would look something like:

    // wrong code, just a wild guess.
UFUNCTION(BlueprintCallable, Category = "Online.Hello.hello")
static TFuture<FString>  SendHello(FString Message);