[peterwaller]

Semaphore, I'm suggesting:

  Block on N-Semaphore, with timeout
  Do timeout upload
  Replace N-Semaphore

If you don't always replace the semaphore, that's a bug.

Queue: I'm just comparing to what the article does. It already has contention on a queue (the chan), it's just the chan-chan-Worker rather than chan-Job. In practice, go channels happily handle millions of messages contending to multiple workers just fine. Consider this test example where you aren't even actually burning any CPU to perform the work:

    package main
    
    func main() {
        q := make(chan int)    
        for i := 0; i < 10; i++ {    
                go func() {    
                        for x := range q {    
                                x = x * 10    
                        }    
                }()    
        }    
    
        for i := 0; i < 1000000; i++ {    
                q <- i    
        }    
    }

On my laptop, it runs in 0.333s single core, and it's slightly slower when you set GOMAXPROCS > 1. But not much slower, the total runtime goes to 0.4-0.5s or so. (Measured with go 1.4). As soon as you do any actual work with the messages you are passing around, the overhead of locking will be lost in the noise.