@MainActor
class Settings {
    private static var values = [String: Any]()

    public static subscript(_ name: String) -> Any? {
        get {
            return values[name]
        }
        set {
            print("Adding \(name): \(newValue ?? "nil")")
            values[name] = newValue
        }
    }
}

Settings["host"] = "192.168.100.1"
Settings["port"] = 3306

print("host is", Settings["host"]!)