Deadlock in GoLang: Why Range Over a Buffered Channel?

When using buffered channels in GoLang, it's important to avoid creating a deadlock situation. A recent issue raised concerns about a deadlock encountered while attempting to range over a buffered channel after all goroutines had completed.

The provided code attempts to use a buffered channel with a capacity of 4 and spawn 4 goroutines that send data to the channel. However, the deadlock occurs because:

• The channel size is too small, resulting in blocked goroutines waiting to write to the full channel.
• The range over operation on the channel remains indefinitely waiting for elements to arrive, while no goroutines are left to write.

Solution 1: Expand Channel Size and Close After Completion

To resolve the deadlock, the channel can be increased in size and closed after all goroutines have completed:

ch := make(chan []int, 5)
...
wg.Wait()
close(ch)

However, this eliminates the benefits of pipelining, as it prevents printing until all tasks are finished.

Solution 2: Signal Completion from within Printing Routine

To enable actual pipelining, the Done() function can be called within the printing routine:

func main() {
    ch := make(chan []int, 4)
    ...
    go func() {
        for c := range ch {
            fmt.Printf("c is %v\n", c)
            wg.Done()
        }
    }()
    ...
}

This approach ensures that the Done() function is only called after each element has been printed, effectively signaling the completion of each goroutine.