Convert Interface{} to Map?

Question

go

Good evening of the day!
Tell me please. There is the following code and the following structure:

func AddToMap(decoded interface{}) (map[string]interface{}) {
  v := reflect.ValueOf(decoded)
  if v.Kind() == reflect.Map {
    for t, key := range v.MapKeys() {
      strct := v.MapIndex(key)
      if key.Interface().(string) == "KeyN" {
        (///////-----///////)?????
      }
    }
  }
  return UserData
}

Пример структуры:
Map["key1":"value1", map["key2"]:{"value2, ... ,valueN"}, .... , map["KeyN":[map["NeedKey"]:{"NeedValue1, NeedValue2"}]]....]

After getting all the map, I need to get further to the map with the "NeedKey" key.
It is of type Interface{} and I have not found a way to iterate over the values ​​of this map.
Translation using:

k := reflect.ValueOf(strct)
for _, values:= range k.MapKeys() {
.....
}

results in an error.
Please help and some clarification.