code: func ExtractPayloadOrPanic(envelope *cb.Envelope) *cb.Payload {
  	payload, err := ExtractPayload(envelope)
  	if err != nil {
  		panic(err)
  	}
  	return payload
  }
docs: // ExtractPayloadOrPanic retrieves the payload of a given envelope and
  // unmarshals it -- it panics if either of these operations fail