I modified the code to include the data structure for the monthly expected total income reports. Here's the updated part of the code that handles this:

// ...
type MonthData struct {
	GroupData map[string]float64
}

var monthlyData = make(map[string]MonthData)

for i := 1; i < 13; i++ {
	// ...

	for _, group := range customProductGroups {
		// ...

		if len(groupServices) > 0 {
			var totalAmount float64
			for _, service := range groupServices {
				// ...
			}

			// Store the total amount for the group in the map
			if _, ok := monthlyData[turkishMonths[i]]; !ok {
				monthlyData[turkishMonths[i]] = MonthData{
					GroupData: make(map[string]float64),
				}
			}
			monthlyData[turkishMonths[i]].GroupData[group.Name] = math.Round(totalAmount*100) / 100
		}
	}
}

// Now the monthlyData map contains the required data structure

Rent this identity for $5/month