Why Does My Go Program Stall Even When All Goroutines Have Finished? A Guide to sync.WaitGroup and Channel Blocking.

Confused About Goroutine Exit: Unveiling the Mystery of sync.WaitGroup and Channel Blocking

In Go, managing concurrency with sync.WaitGroup and channels is a common practice. However, for beginners, it can be puzzling when a program stalls despite fulfilling goroutine completion expectations. Let's delve into a specific case and unravel the underlying issue.

The Problem

A developer implemented a program utilizing sync.WaitGroup and a channel (fetchedSymbols) to retrieve a list of stock quotes concurrently. While the program waited for goroutines to complete, it refused to terminate.

Understanding the Issue

The root of the problem lies in the omission of closing the fetchedSymbols channel. When iterating over this channel in the main function, the program becomes indefinitely blocked. In this case, closing the channel should be initiated upon the completion of all goroutines.

Solution

To ensure smooth program execution, the developer introduced a helper goroutine that monitors the sync.WaitGroup and triggers the closure of fetchedSymbols once all goroutines have concluded their tasks. This eliminated the blocking behavior and allowed the program to exit gracefully.

Implementation

<code class="go">go func() {
    wg.Wait()
    close(fetchedSymbols)
}()

for response := range fetchedSymbols {
    fmt.Println("fetched " + response)
}</code>

By implementing this solution, the program now gracefully exits after successfully downloading all stock quotes, efficiently utilizing Go's concurrency features.

The above is the detailed content of Why Does My Go Program Stall Even When All Goroutines Have Finished? A Guide to sync.WaitGroup and Channel Blocking.. For more information, please follow other related articles on the PHP Chinese website!