Swift JSON decode

gistfile1.txt

struct Event: Decodable {
        let id: String
        let event: String
        let data: [[Int]]?
        let date: String?
    }
func decode() {
    let json = """
            {
            "id": "b1afdc30-47e7-11e8-8931-33f1426b7c32",
            "event": "move",
            "data" : [[1,1]],
            "date" : "\(Date())"
            }
            """.data(using: .utf8)!
    guard let event = try? JSONDecoder().decode(Event.self, from: json) else {
        print("Error: Message format not known")
        return
    }
    print(event)
}