Simple Concurrency

Question

Can someone explain how this works:

package main

import (
    "fmt"
    "time"
)

func say(s string) {
    for i := 0; i < 5; i++ {
        time.Sleep(100 * time.Millisecond)
        fmt.Println(s)
    }
}

func main() {
    say("world")
}

But this doesnt work once i add the word go to the routine in main

package main

import (
    "fmt"
    "time"
)

func say(s string) {
    for i := 0; i < 5; i++ {
        time.Sleep(100 * time.Millisecond)
        fmt.Println(s)
    }
}

func main() {
    go say("world")
}

I think its because its finishing before executing the goroutine.

Correct. As soon as `main` returns, the program exits, regardless of any other goroutines that may be running. — Adrian, Jun 08 '18 at 16:05
That depends on your actual use case. In this example case you just wouldn't run it in a goroutine because there's no reason to. — Adrian, Jun 08 '18 at 16:06

IceLady · Accepted Answer · 2018-06-08T16:12:10.787

3

The "world" goroutine does not run or complete because main returns and the program exits.

When that function invocation returns, the program exits. It does not wait for other (non-main) goroutines to complete. https://golang.org/ref/spec#Program_execution

edited Jun 08 '18 at 16:12

answered Jun 08 '18 at 16:08

IceLady

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Simple Concurrency

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