DNS记录类型

// Encoding a message
let request = Message(
    type: .query,
    questions: [Question(name: "apple.com.", type: .pointer)]
)
let requestData = try request.serialize()

// Not shown here: send to DNS server over UDP, receive reply.

// Decoding a message
let responseData = Data()
let response = try Message.init(deserialize: responseData)
print(response.answers.first)