Golang find a value from a map of nested json data from MongoDB

I am trying to receive data from my MongoDB using MGO in a map of type []map[string]interface{}

My JSON looks like this -

{
   "_id":"string",
   "brandId":123,
   "category":{
      "television":[
         {
            "cat":"T1",
            "subCategory":[
               {
                  "subCat":"T1A TV",
                  "warrantyPeriod":6
               }
            ],
            "warrantyPeriod":12
         },
         {
            "cat":"T2",
            "subCategory":[
               {
                  "subCat":"T2A",
                  "warrantyPeriod":18
               },
               {
                  "subCat":"T2B",
                  "warrantyPeriod":9
               }
            ],
            "warrantyPeriod":15
         },
         {
            "cat":"T3",
            "subCategory":[
               {
                  "subCat":"T3A",
                  "warrantyPeriod":3
               },
               {
                  "subCat":"T3B",
                  "warrantyPeriod":5
               },
               {
                  "subCat":"T3C",
                  "warrantyPeriod":7
               },
               {
                  "subCat":"T3D",
                  "warrantyPeriod":11
               }
            ],
            "warrantyPeriod":4
         }
      ],
      "television_warrantyPeriod":24
   },
   "title":"BrandName"
}

I would ideally pass in the category name i.e. 'television' and cat and subCat values which could be optional.

For e.g. something like this -

{
"categorySlug": "television",
"brandId": "123",
"model": "T2"
}

In which case I would expect to find '15' which is the warrantyPeriod value for T2 if there are no T2A or T2B specified.

My query functions look like this -

var data map[string]string
err := json.NewDecoder(r.Body).Decode(&data)
log.Println(err)
var buffer bytes.Buffer
buffer.WriteString("category.")
buffer.WriteString(data["categorySlug"])
brandId, _ := strconv.Atoi(data["brandId"])
concernedbrandandcategory := database.GetMappedFields("Brands", bson.M{"brandId": brandId, buffer.String(): bson.M{"$exists": true}}, bson.M{buffer.String(): 1})
categorymap := concernedbrandandcategory[0]
log.Println(categorymap["category"]["television"], reflect.TypeOf(categorymap))

My GetMappedFields function looks like this -

func GetMappedFields(collectionName string, query interface{}, selector interface{}) (result []map[string]interface{}) {
	MgoSession.DB(Dbname).C(collectionName).Find(query).Select(selector).All(&result)
	return
}

I'm just not able to wrap my head around this nested structure which sometimes returns a map and sometimes an interface!
Any help would be highly appreciated!

you can do something like this

    majorCat := body["categorySlug"]
	category := body["category"]
	subCategory := body["subCategory"]
	brandId, err := strconv.Atoi(body["brandId"])
	if err != nil {
		log.Println(err)
	}
	result := database.GetMappedFields("Brands", bson.M{"brandId": brandId}, bson.M{"category": 1, "_id": 0})
	internalObj := result[0]["category"].(map[string]interface{})
	finalValue := internalObj["television_warrantyPeriod"]
	if category != "" {
		for _, v := range internalObj[majorCat].([]interface{}) {
			subObj := v.(map[string]interface{})
			if subObj["cat"] == category {
				finalValue = subObj["warrantyPeriod"]
				if subCategory != "" {
					minorObj := subObj["subCategory"].([]interface{})
					for _, iter := range minorObj {
						kevVal := iter.(map[string]interface{})
						if kevVal["subCat"] == subCategory {
							finalValue = kevVal["warrantyPeriod"]
						}
					}
				}
			}
		}
	}

Hopefully this will do dynamically or you can create a struct so that it can directly be decoded into that cheers