code: func FromContext(ctx context.Context) error {
  	e := ctx.Err()
  	if e == nil {
  		return nil
  	}
  
  	if e == context.Canceled {
  		return Cancelled(e)
  	}
  	if e == context.DeadlineExceeded {
  		return Deadline(e)
  	}
  	return Unknown(e)
  }
docs: // FromContext returns the error class from the passed in context