如何正确使用通道实现并发POST API调用和数据录入文件

func callAPI(url string, data string, resultChan chan<- string) {
    resp, err := http.Post(url, "application/json", strings.NewReader(data))
    if err != nil {
        resultChan <- err.Error()
        return
    }
    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        resultChan <- err.Error()
        return
    }

    resultChan <- string(body)
}

func writeToFile(filePath string, data string, resultChan chan<- string) {
    file, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
    if err != nil {
        resultChan <- err.Error()
        return
    }
    defer file.Close()

    _, err = io.WriteString(file, data)
    if err != nil {
        resultChan <- err.Error()
        return
    }

    resultChan <- "Data written to file successfully"
}

func main() {
    url := "https://example.com/api"
    data := "..."
    filePath := "data.txt"

    resultChan := make(chan string)
    var wg sync.WaitGroup

    wg.Add(2)
    go func() {
        defer wg.Done()
        callAPI(url, data, resultChan)
    }()

    go func() {
        defer wg.Done()
        writeToFile(filePath, data, resultChan)
    }()

    go func() {
        wg.Wait()
        close(resultChan)
    }()

    for result := range resultChan {
        fmt.Println(result)
    }
}