需求是这样的：需要查询数据库里面的数据，然后生成对应格式的xml，打算用协程实现，我的大致思路是这样的：查询出总数据量，然后根据配置的每个xml的数据个数，计算出需要生成多少个xml，每个xml就启动一个协程去执行生成xml，代码已经写完，但是经常跑一会就卡主不执行了。。不知道为啥，有大神指导一下，或者提供一个更加好的思路么，数据量不多，26万条左右。。如下是协程代码：

func getSiteMaps(db *sql.DB, offset int64, size int64, c chan Sitemap) {
    fmt.Println("offset in channel:", offset)
    sql := "select a.id as outerID,a.name,a.sale_price as price, a.category_id,a.market_price as value,b.name as brand from item as a left join item_brand as b on a.brand_id = b.id where a.status = 1 order by a.id asc limit " + strconv.FormatInt(offset, 10) + "," + strconv.FormatInt(size, 10)
    var r Urlset   //初始化xml
    var urls []Url //初始化urls
    //查询具体的数据
    if rows, rowsErr := db.Query(sql); rowsErr != nil {
        panic(rowsErr)
    } else {
        for rows.Next() {
            var (
                outerID, name, brand, category_id string
                price, value                      float64
            )
            rows.Scan(&outerID, &name, &price, &category_id, &value, &brand)
            if outerID == "" {
                continue
            }
            //loc获取
            _loc := getLocUrl(outerID)
            //通过categoryId获取分类信息
            _categoryInfo := getCategoryInfoByParentId(category_id, db)
            // fmt.Println(_categoryInfo)
            // os.Exit(1)
            if _categoryInfo["categoryId"] == "" {
                continue
            }
            //获取商品图片
            _imgs := getImages(outerID, db)
            if len(_imgs) <= 0 {
                continue
            }
            _firstImg := ""
            var _moreImages []Images
            for i, v := range _imgs {
                if i == 0 {
                    _firstImg = v
                } else {
                    _moreImages = append(_moreImages, Images{InnerText: v, Index: i})
                }
            }
            moreImages := Mimages{Img: _moreImages}
            // moreImages := _moreImages
            subAttribute := []SubAttribute{SubAttribute{Key: "ext_down_load", Value: "https://m.mia.com/detail-a-" + outerID + ".html"}, SubAttribute{Key: "ext_put_url", Value: "https://m.mia.com/detail-a-" + outerID + ".html"}}
            //Data数据
            _choice := Attribute{Attribute: subAttribute}
            itemData := Data{
                OuterID:          outerID,
                Name:             name,
                Price:            price,
                Value:            value,
                PriceUnit:        _PRICE_UNIT,
                Availability:     _AVAILABILITY,
                Image:            _firstImg,
                MoreImages:       moreImages,
                Brand:            brand,
                Loc:              _loc,
                PcLoc:            getPcLoc(outerID),
                SellerSiteUrl:    _SELLER_SITE_URL,
                ShopName:         _SHOP_NAME,
                SearchWiseUrl:    getSearchWiseUrl(outerID),
                Category:         _categoryInfo["categoryName"],
                CategoryUrl:      getCategoryUrl(category_id),
                CategoryPcUrl:    getCategoryPcUrl(category_id),
                SubCategory:      _categoryInfo["subCategoryName"],
                SubCategoryUrl:   getCategoryUrl(_categoryInfo["subCategoryId"]),
                SubcategoryPcUrl: getCategoryPcUrl(_categoryInfo["subCategoryId"]),
                Choice:           _choice,
                SellerName:       _SELLER_NAME,
                Logo:             _LOGO}
            // fmt.Println(itemData)
            // os.Exit(1)
            //url数据
            itemUrl := Url{Loc: _loc, Data: itemData}
            //urls数据
            urls = append(urls, itemUrl)

        }
        //生成xml数据
        r.Url = urls
    }
    //生成xml文件
    if len(urls) > 1 {
        //取数据,
        fileName := getXmlName(offset, size)
        generateXml(fileName, r, func() {
            xmlUrl := _URL_PREFIX + fileName
            itemSiteMap := Sitemap{Loc: xmlUrl, Lastmod: getCurrentTime()}
            // sitemap = append(sitemap, itemSiteMap)
            //需要停顿几秒，待写文件完毕。主要是防止最后一次写文件没写完，程序就执行完退出
            time.Sleep(5)
            fmt.Println("done...", offset)
            c <- itemSiteMap
        })
    }
}

如下是main里面的内容：

func main() {

    db, dbErr := sql.Open("mysql", _DB)
    if dbErr != nil {
        fmt.Println("db connection err")
        os.Exit(1)
    } else {
        fmt.Println("db ok")
    }
    sql2 := "select count(*) as total from item as a left join item_brand as b on a.brand_id = b.id where a.status = 1"
    var total float64
    if rowCountErr := db.QueryRow(sql2).Scan(&total); rowCountErr != nil {
        panic(rowCountErr)
    } else {
        fmt.Println("total:", total)
        //根据条数，获取协程数量
        pages := int(math.Ceil(total / _NUM_PER_XML))
        ch := make(chan Sitemap, pages)
        for i := 0; i <= pages; i++ {
            var offset int64
            if i > 0 {
                offset = int64(_NUM_PER_XML*i + 1)
            }
            go getSiteMaps(db, offset, _NUM_PER_XML, ch)
        }
        for v1 := range ch {

            fmt.Println("val:", v1)
        }
    }
}

新手，求指导？