为什么此go代码不使用goroutine打印任何内容[重复]

Question

This question already has an answer here:

• No output from goroutine in Go 3 answers

I must be missing something really basic about goroutines, but I've looked around and I cannot see any reason why this would not work...

package main

import "fmt"

func main() {
    for i := 0; i < 20; i++ {
        //fmt.Println(i)
        go func(j int) {
            fmt.Println(j + 100)
        }(i)
    }
}

</div>

Answer 1

Your program is finishing before your goroutines have a chance to run.

Here's your code with a WaitGroup:

package main

import (
    "fmt"
    "sync"
)

func main() {
    var wg sync.WaitGroup
    for i := 0; i < 20; i++ {
        wg.Add(1)
        go func(j int) {
            defer wg.Done()
            fmt.Println(j + 100)
        }(i)
    }
    fmt.Println("Waiting...")
    wg.Wait()
    fmt.Println("Done.")
}

https://play.golang.org/p/lmCPU9-qkB