Decoding Codable Throwing Nil Key not found

I am trying to encode and decide the data and encoding working perfectly fine but when i use Decoder to decode the data , my decoder function is throwing me an error . Please look at my code and let me know what should i do in order to properly decode the data . The issue after debugging I found is decoder block does not proceed further next to switch , instead on type it returns and error with , DecodingKey type not found.

type = try container.decode(WorkoutType.self, forKey: .type) this is the line where it does not proceed further when i wanna decode the data.

here is my code

struct OverviewWorkout : Codable {

enum WorkoutType: String , Codable {
    case workout
    case coach
    case bodyArea
    case challenge
    case title
    case group
    case trainer
}


enum WorkoutsData  {
  case workout(Workout)
  case challenge(Workout)
  case group([Workout])
  case trainer([Trainer])
  case bodyArea([Workout])
  case coach(CoachInstruction)
  case title(Title)

}

var type: WorkoutType
var data : WorkoutsData

init(from decoder: Decoder) throws {
    print("decoder called")
    let container = try decoder.container(keyedBy: CodingKeys.self)
    type =  try container.decode(WorkoutType.self, forKey: .type)
    switch type {
    case .workout, .challenge:
        let data = try container.decode(Workout.self, forKey: .data)
        self.data = .workout(data)
    case .coach:
        let data = try container.decode(CoachInstruction.self, forKey: .data)
        self.data = .coach(data)

    case .bodyArea:
        let data = try container.decode([Workout].self, forKey: .data)
        self.data = .bodyArea(data)

    case .title:
        let data = try container.decode(Title.self, forKey: .data)
        self.data = .title(data)

    case .group:
       let data = try container.decode([Workout].self, forKey: .data)
        self.data = .group(data)

      // trainer data
        case .trainer:
          let  data = try container.decode([Trainer].self, forKey: .data)
            self.data = .trainer(data)

        }

        print("decodable called")
        
    }
    


    private enum CodingKeys: String, CodingKey {
        case type,data

    }
}

extension OverviewWorkout {
    struct Title: Codable {
        let title: String
    }
}


extension OverviewWorkout {
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        print(container)
        switch data {
        case .workout(let workout):
            try container.encode(workout, forKey: .data)
        case .bodyArea(let bodyarea):
            try container.encode(bodyarea, forKey: .data)
        case .title(let title):
            try container.encode(title, forKey: .data)
        case .coach(let coach):
            try container.encode(coach, forKey: .data)
        case .trainer(let trainer):
            try container.encode(trainer, forKey: .data)
        case .group(let group):
            try container.encode(group, forKey: .data)

        default:
            print("out of range")
        }
      }
}

here is the error I am having whenever init(from decoder: Decoder) throws is called keyNotFound(CodingKeys(stringValue: "type", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: "type", intValue: nil) ("type").", underlyingError: nil)) keyNotFound(CodingKeys(stringValue: "type", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: (lldb)