code: func ExposeStackTrace(err error) error {
  	if err == nil {
  		return err
  	}
  
  	st, ok := getStackTracer(err)
  	if !ok {
  		return err
  	}
  
  	return &withStack{
  		err: err,
  		st:  st,
  	}
  }
docs: // ExposeStackTrace exposes the stack trace (if any) in the outer error.