为什么我完全相同的go例程混乱？

Question

I've got the following go code executing routines.

package main

import (
        "fmt"
        "time"
)

func count(id int) {
        for i := 0; i < 10; i++ {
                fmt.Println(id, ":", i)
                time.Sleep(time.Millisecond * 1000)
        }   
}

func main() {
        for i := 0; i < 10; i++ {
                go count(i)
        }   
        time.Sleep(time.Millisecond * 11000)
}

I would expect the output to be:

1 : 0
2 : 0
3 : 0
4 : 0
5 : 0
6 : 0
7 : 0
8 : 0
9 : 0
1 : 1
2 : 1
3 : 1
4 : 1
etc...

but instead, I get:

0 : 0
6 : 0
7 : 0
5 : 0
8 : 0
9 : 0
3 : 0
2 : 0
4 : 0
1 : 0
5 : 1
6 : 1
7 : 1
1 : 1
8 : 1
etc...

Why are they not in order of the original, outside for loop executing the count method? Why are some count methods getting out of sync?

Answer 1

When a goroutine executes is out of the control of the programmer. You have some control if you use signals via channels and sync.WaitGroup, (like having one goroutine wait until another has finished) but you cannot control the execution order of goroutines