I have a sample JSON that I am trying to decode to models in my Swift. But it keeps failing and giving me error:

Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.typeMismatch(Swift.Array, Swift.DecodingError.Context(codingPath: [],
 debugDescription: "Expected to decode Array but found a dictionary instead.", underlyingError: nil))
struct HTTPClient {
    
    func fetchMessages() async throws -> [MessageType: [Message]] {
        let (data, _) = try await URLSession.shared.data(from: Constants.Urls.Messages)
        return try JSONDecoder().decode([MessageType: [Message]].self, from: data)
    }

}

enum MessageType: String, CaseIterable, Codable {
    case onBudgetCreated = "onBudgetCreated"
}

struct Message: Decodable {
    let title: String
    let text: String
    let image: URL
}

Here is the JSON I am decoding: 

{
  "onBudgetCreated": [
    {
      "title": "You Made a Budget?",
      "text": "Some text.",
      "image": "https://example.com/images/someimage.png"
    },
    {
      "title": "Good work",
      "text": "something here",
      "image": "https://example.com/images/someimage.png"
    }
  ]
}

Does anyone see any issue, what am I doing wrong?