code: func Unwrap(err error) error {
  	for {
  		wrap, ok := err.(Wrapped)
  		if !ok {
  			return err
  		}
  
  		inner := wrap.InnerError()
  		if inner == nil {
  			break
  		}
  		err = inner
  	}
  	return err
  }
docs: // Unwrap unwraps a wrapped error recursively, returning its inner error.
  //
  // If the supplied error is not nil, Unwrap will never return nil. If a
  // wrapped error reports that its InnerError is nil, that error will be
  // returned.