best way to add option validator

What is the best way to add a validator for option parse? Is "AddValidator" best here? How is to allow await statement inside validator logic that makes a db call suppose?? It works for sync but not async - maybe delegate needs to be wrapped .. could not get an example, so reaching for help.

```
var coption = new Option("-c");
coption.FromAmong>("-", ".", "_");
coption.AddValidator(symbol => {
var pvalue = symbol.GetValueOrDefault();
//await Task.Delay(2000);
// logic for pvalue check
return null;
});
```

Looking forward for suggestion!