Errors returned from Join are incompatible with errors returned the standard lib's errors.Join

The standard errors package uses the following example to extract the individual sub-errors from the result err of calling Join:

https://pkg.go.dev/errors#Join
`fmt.Println(err.(interface{ Unwrap() []error }).Unwrap())`

This is not possible with return values of Join:
`panic: interface conversion: *withstack.withStack is not interface { Unwrap() []error }: missing method Unwrap`

However the code needed to do the same is, unintuitively:
`fmt.Println(err.(interface{ Unwrap() error }).Unwrap().(interface{ Unwrap() []error }).Unwrap())`

Or is there a better way do it?

Start with the Join implementation and the withStack unwrapping behavior, then compare the result with the standard library errors.Join example linked in the issue. Confirm how callers can reach the individual sub-errors, and consider the work complete when Join results support the standard Unwrap() []error extraction pattern or the project documents the intended alternative.

Rédigé par le modèle d'indexation à partir du texte de l'issue.