should I pass functions as parameter of a go routine?

[Julien Pivotto]

Hello,

In the following example: https://play.golang.org/p/yz_ifHC-Hut

for _, onedoer := range d {

  go onedoer.do(&wg)

}

Should I pass the function onedoer.do as a parameter of the go routine:  https://play.golang.org/p/WHPahoayDbM ?

for _, onedoer := range d {

  go func(od *doer, w *sync.WaitGroup) {

    od.do(w)

  }(onedoer, &wg)

}

I am wondering if `go func()` could return before figuring out which function to run, creating a race with the loop.

Thanks in advance!

[Axel Wagner]

Interesting question. I think the code is fine. From the spec:

> The function value and parameters are evaluated as usual in the calling goroutine, but unlike with a regular call, program execution does not wait for the invoked function to complete.

This means `onedoer.do` is immediately evaluated, before the loop continues. The usual issue with loops is due to closures. So, this would be wrong and have exactly the issue you are worried about:

for _, onedoer := range d {

    go func() { oneoder(&wg) }

}

But the go statement isn't equivalent to that, it doesn't close over the function value, it evaluates it.

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[Julien Pivotto]

Thank you for your quick answer, it is of a great help.

have a nice day.

[Max Renaud]

In your second example, the address of wg doesn't change with each iteration so you can use:

for _, onedoer := range d {

go func(od *doer) {

od.do(&wg)

}(onedoer)

}

https://play.golang.org/p/A1dAUuyvg9T