从goroutine捕获返回值

Question

The below code gives compilation error saying 'unexpected go':

x := go doSomething(arg)

func doSomething(arg int) int{
    ...
    return my_int_value
}

I know, I can fetch the return value if call the function normally, without using goroutine. Or I can use channels etc.

My question is why is it not possible to fetch a return value like this from a goroutine.

Answer 1

The strict answer is that you can do that. It's just probably not a good idea. Here's code that would do that:

var x int
go func() {
    x = doSomething()
}()

This will spawn off a new goroutine which will calculate doSomething() and then assign the result to x. The problem is: how are you going to use x from the original goroutine? You probably want to make sure the spawned goroutine is done with it so that you don't have a race condition. But if you want to do that, you'll need a way to communicate with the goroutine, and if you've got a way to do that, why not just use it to send the value back?