UnaryVoidDelegateFutureOr<T> typedef
UnaryVoidDelegateFutureOr<T> = UnaryDelegateFutureOr<void, T>
a typedef for an UnaryDelegateAsync that returns a Future<void>
Implementation
typedef UnaryVoidDelegateFutureOr<T> = UnaryDelegateFutureOr<void, T>;