@RestResource(urlMapping='/api/*')

@HttpGet
global static List<Wrapper1> getDetails() {
    RestRequest req = RestContext.request;
    RestResponse res = RestContext.response;

    string GO, ID;

    if(!string.isEmpty(req.params.get('GO'))){
        GON = req.params.get('GO');
    }
    else{
        throw new Utility.applicationException('GO Cannot be null');
    }

    if(!string.isEmpty(req.params.get('ID'))){
        UCMID = req.params.get('ID');
    }
    else{
        ID = '';
    }

    List<Wrapper1> Details = fetchDetails(GO, ID);
    return Details;
}

global class Wrapper1 {
@AuraEnabled
public string GO;
@AuraEnabled
public string Name;
@AuraEnabled
public string Address;
@AuraEnabled
public List<Wrapper2> Fsets;
public class OrderTrackingDetail{
    @AuraEnabled public string Carrier=System.label.CCP_NotAvailableValue;
    @AuraEnabled public string TrackingID=System.label.CCP_NotAvailableValue;
    @AuraEnabled public string fSetNum;
    @AuraEnabled public string trackingURL;
}

public class Wrapper2 implements Comparable {

public string addressCity;
@AuraEnabled
public string addressLine1;
@AuraEnabled
public string addressLine2;
@AuraEnabled
public string addressLise3;
public string addressLine4;
public string addressState;
public string addressZip;
public string Name;
public string Country;
@AuraEnabled
public List<Object> object1 = new List<Object>();
@AuraEnabled
public List<Object> object2 = new List<Object>();
public Integer compareTo(Object objToCompare) {
    integer val1 = integer.valueOf(//something);
    integer val2 = integer.valueOf(((Wrapper2)objToCompare).//something);
    if (val1 == val2)
        return 0;
    if (val1 > val2)
        return 1;
    return -1;
}