Why does using a copy of Sync.WaitGroup in an external function lead to missing output in a goroutine?

Using Sync.WaitGroup with External Functions

In the code provided, the intention is for the primary goroutine to print numbers from 1 to 11 by utilizing a channel and a wait group. However, it occasionally skips number 11, resulting in an incomplete output.

The issue arises from the incorrect传递 of sync.WaitGroup to the external function, Print. By passing a copy of WaitGroup to the function, it can't perform the necessary Done() call on the original wait group being waited on by the main goroutine.

Best Solution:

The recommended solution involves modifying the code as follows:

<code class="go">func main() {
    ch := make(chan int)

    var wg sync.WaitGroup
    wg.Add(2)

    go Print(ch, &wg)

    go func() {
        for i := 1; i <p>In this fix, the Print function receives a pointer to the wait group, ensuring that its Done() method is called within the function, thus allowing the main goroutine to proceed correctly.</p>
<p><strong>Alternative Solution:</strong></p>
<p>Alternatively, one can eliminate the need for WaitGroup within the Print function by directly closing the channel after sending all numbers:</p>
<pre class="brush:php;toolbar:false"><code class="go">func Print(ch <p>In this case, the main goroutine must wait on the channel's closure instead:</p>
<pre class="brush:php;toolbar:false"><code class="go">wg.Wait()
close(ch)</code>

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