whenComplete method
Implementation
FutureOr<T> whenComplete(FutureOr<void> Function() action) {
final that = this;
if (that is Future<T>) {
return that.whenComplete(action);
}
final f = action();
if (f is Future) {
return f._innerThen((_) => that, onError: (e) => that);
}
return that;
}