使用Go和Waitgroups并行获取数据

I have a method that queries an API to obtain data for different date ranges with or without a filter.

func getTopData(country string, startDate time.Time, endDate time.Time, filterID uint) (result map[string][10]topResult) {
    response := getRequest(fmt.Sprintf("%s/top/%s/%s-%s/filterid:%d/10",
        cfg.API.URI,
        country,
        startDate.Format("20060102"),
        endDate.Format("20060102"),
        filterID))

    json.Unmarshal(response, &result)
    return
}

Each call takes about one minute to finish and I need to call the method six times with different parameters (for each of the last three months without filter and each of the last three months with filter).

So now I have something like this:

var topData [6]map[string][10]topResult
topData[0] = getTopData(country, firstMonthStart, firstMonthEnd, 0)
topData[1] = getTopData(country, secondMonthStart, secondMonthEnd, 0)
topData[2] = getTopData(country, thirdMonthStart, thirdMonthEnd, 0)
topData[3] = getTopData(country, firstMonthStart, firstMonthEnd, filterID)
topData[4] = getTopData(country, secondMonthStart, secondMonthEnd, filterID)
topData[5] = getTopData(country, thirdMonthStart, thirdMonthEnd, filterID)

With this, the data is filled one after another. How would I go to make the calls in parallel while maintaining the order of the results in the topData array (so that the data at index 0 is for the first month without filter, data at index 4 is the second month with filter, etc.)?

I was thinking about using a WaitGroup, but I am not really sure how to handle the actual result data. :(

So, first thing would be adding wg *sync.WaitGroup as parameter to the getTopData function. Inside I do a wg.Add(1) and defer wg.Done(). Outside the function, I do var wg sync.WaitGroup and pass &wg to getTopData, do my six calls and then wg.Wait(). But how do I assign the results to topData[0], topData[1], etc.?

I went ahead and did the following changes:

1. getTopData has a parameter result *map[string][30]topResult
2. I removed the return type of getTopData
3. I am calling getTopData six times and pass &topData[0], &topData[1], etc. as parameter