create static method
Create a Future from scratch.
await F4.create((resolve, reject)=>()=>resolve(1));
Implementation
static Future create(Function fn) {
final completer = Completer();
Function.apply(fn, [
([dynamic data]) => completer.complete(data),
([Object? e, StackTrace? s]) =>
completer.completeError(e ?? RejectionError(), s)
]);
return completer.future;
}