A db connection that appears dial tcp: lookup xxx.com: no such host? when there are a large number of queries

the program code snippet looks like this:

maxPage := *flagMaxPage
        if maxPage > 0 {
            jobs := make(chan int, maxPage)
            results := make(chan []map[string]string, maxPage)
            // 10jobsresults
            for w := 1; w <= 10; wPP {
                go doWork(jobs, results)
            }
            //
            for j := 1; j <= maxPage; jPP {
                jobs <- j
            }
            close(jobs)
            //db connect
            db, err := mysqlUtil.CreateReadDb()
            defer db.Close()
            if err != nil {
                log.Fatal("connect db err ", err)
                fmt.Println("connect db err ", err)
            }
            //
            for j := 1; j <= maxPage; jPP {
                data := <-results
                //
                doDb(db, data)
                fmt.Println(len(data))
            }
            close(results)
            fmt.Println("all done...")
        }

The

doDb function is as follows:

func doDb(db *sql.DB,data []map[string]string) {
    if data != nil {
        for _, v := range data {
            if v == nil {
                continue
            }
            if v["title"] == "" {
                continue
            }
            if v["url"] == "" {
                continue
            }
            //
            sqlStr := `select * from film where title_md5 ="` + Md5(v["title"]) + `"`
            rows, err := db.Query(sqlStr)
            if err != nil {
                fmt.Println("query err1 ", err)
                continue
            }
            existData, err := mysqlUtil.GetRow(rows)
            if err != nil {
                fmt.Println("query err2 ", err)
                continue
            }
            //,
            if len(existData) == 0 {
                score := v["score"]
                scoreVal, err := strconv.ParseFloat(score, 64)
                if err != nil {
                    fmt.Println("insert data parse score error ", err)
                    continue
                }
                f1 := decimal.NewFromFloat(scoreVal)
                f2 := decimal.NewFromFloat(100)
                aaa := f1.Mul(f2).IntPart()
                insertScore := strconv.Itoa(int(aaa))
                titleMd5 := Md5(v["title"])
                sqlInsert := `insert into film(title, img, uptime, url, score, title_md5) values ("` + v["title"] + `", "` + v["img"] + `", "` + v["uptime"] +
                    `","` + v["url"] + `","` + insertScore + `","` + titleMd5 + `")`
                db.Query(sqlInsert)
            }
        }
    }
}

after testing, about 20, err) runs. The second parameter of doDb function can contain up to 15 data at a time. After executing the results of 16 co-runs, a large number of data will be reported in fmt.Println ("query err1", err)).

query err1  dial tcp: lookup xxxx.com: no such host

when I package this error, I execute

manually

nslookup xxxx.com

parsing is normal. Excuse me, why is this? DoDb this function is an one to deal with result, a total of only 20 records 15, why there is such a problem?

Golang

Apr.06,2021