Replace WaitGroup using semaphore instead

[godoylucase]

No description provided.

[peterbourgon]

A semaphore is usually used to constrain the parallelism of a concurrent operation to less than its theoretical maximum concurrency. For example, if you need to make a bunch of GET requests, but only want 3 in-flight at once, you might do

semaphore := make(chan struct{}, 3)
for _, url := range urls {
    go func(url string) {
        semaphore <- struct{}{} // acquire
        defer func() { <-semaphore }() // release
        resp, err := http.Get(url)
        // ...
    }(url)
}

Semaphores just have those two operations — acquire, and release. I think you misinterpret the Wiki definition when it mentions wait — that doesn't map to an operation, but rather describes what happens when a goroutine tries to acquire on a semaphore that's already at capacity.

What you've created here isn't precisely a semaphore. You're just using a channel as a counter! It works. But I bet there's a much easier way to do what you're trying to do, with a lot less code :)

[godoylucase]

@peterbourgon thanks for your comments, what you said it's right. It is a semaphore hybrid wrapped into a struct. I will try to pull apart the wait method by segregating interfaces. Thanks!