关于goroutine并发的问题

Question

I got some trouble about goroutine concurrent. In my expect, it should run asynchronously and print out almost at same time but what it really did was running with waiting

MyTestCode

package main

type batchD []string
var cBD = make(chan batchD, 6)

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())

    data := [][]string{}
    data = append(data, []string{"71", "40348270", "6", "win888e", "6", "1", "N", "127.0.0.1"})
    data = append(data, []string{"71", "40348270", "6", "win888e", "6", "1", "N", "127.0.0.1"})
    data = append(data, []string{"71", "40348270", "6", "win888e", "6", "1", "N", "127.0.0.1"})
    data = append(data, []string{"71", "129499244", "6", "win888e", "6", "1", "N", "127.0.0.1"})
    data = append(data, []string{"71", "40348270", "6", "win888e", "6", "1", "N", "127.0.0.1"})
    data = append(data, []string{"71", "40348270", "6", "win888e", "6", "1", "N", "127.0.0.1"})

    for k,v := range data {
        go func() {
            fmt.Println(k,v)
            //batchD{}.BatchDeposit(v[0],v[1],v[2],v[3],v[4],v[5],v[6],v[7])
            delay()
            cBD <- data[k]
        }()
        <-cBD
    }
}

func delay() {
    time.Sleep(1 * time.Second)
    t := Basic.NowTime("Taipei")
    fmt.Println(t)
}

Output I got

0 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
1 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:41  
2 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:42  
3 [71 129499244 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:43  
4 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:44  
5 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:45  

Output I Expected

0 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
1 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
2 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
3 [71 129499244 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
4 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  
5 [71 40348270 6 win888e 6 1 N 127.0.0.1]  
2017-08-16 12:00:40  

Any suggestions or tips will helps. Thanks.

Answer 1

Essentially, you have:

var cBD = make(chan batchD, 6)
for k := range data {
    go func() {
        time.Sleep(1 * time.Second)
        fmt.Println(time.Now().Format("2006-01-02 15:04:05"))
        cBD <- data[k]
    }()
    <-cBD
}

Each loop starts a goroutine. The loop then waits, via the channel receive <-cBD, until the goroutine sends to the channel, via cBD <- data[k], one second later. For example,

2017-08-16 02:52:46
2017-08-16 02:52:47
2017-08-16 02:52:48
2017-08-16 02:52:49
2017-08-16 02:52:50
2017-08-16 02:52:51