AlarmMetadata struct

How can AlarmMetadata be implemented?

I have referenced the sample code from "Scheduling an alarm with AlarmKit" and used the following:

import AlarmKit

struct CookingData: AlarmMetadata {
    let createdAt: Date
    /* other properties */

    init() {
        self.createdAt = Date()
        /* other properties here */
    }
}

But it always has the following errors:

Main actor-isolated conformance of 'CookingData' to 'Decodable' cannot satisfy conformance requirement for a 'Sendable' type parameter of 'Self'

Type 'CookingData' does not conform to protocol 'AlarmMetadata'.

However in the sample App, this error is not there.

Any other guidance on AlarmMetadata protocol besides the documentation?