Code returns the Code of the error if it is a Status error, codes.OK if err is nil, or codes.Unknown otherwise.

Convert is a convenience function which removes the need to handle the boolean return value from FromError.

Error returns an error representing c and msg.

Errorf returns Error(c, fmt.Sprintf(format, a...)).

FromContextError converts a context error into a Status.

FromError returns a Status representing err if it was produced from this package or has a method `COAPError() *Status`.

Status holds error of coap.