Discrepancies between Go Playground and Go on my machine?

Question

To settle some misunderstandings I have about goroutines, I went to the Go playground and ran this code:

package main

import (
    "fmt"
)

func other(done chan bool) {
    done <- true
    go func() {
        for {
            fmt.Println("Here")
        }
    }()
}

func main() {
    fmt.Println("Hello, playground")
    done := make(chan bool)
    go other(done)
    <-done
    fmt.Println("Finished.")
}

As I expected, Go playground came back with an error: Process took too long.

This seems to imply that the goroutine created within other runs forever.

But when I run the same code on my own machine, I get this output almost instantaneously:

Hello, playground.
Finished.

This seems to imply that the goroutine within other exits when the main goroutine finishes. Is this true? Or does the main goroutine finish, while the other goroutine continues to run in the background?

Answer 1

What you will see on screen is nondeterministic. Or more precisely if by any chance the true value you pass to channel is delayed you would see some "Here".

But usually the Stdout is buffered, it means it's not printed instantaneously but the data gets accumulated and after it gets to maximum buffer size it's printed. In your case before the "here" is printed the main function is already finished thus the process finishes.

The rule of thumb is: main function must be alive otherwise all other goroutines gets killed.