How Can We Safely Close a Channel After All Goroutines Have Completed Using a WaitGroup?

Close Channel after Goroutine Completion with WaitGroup

When working with channels and goroutines, closing the channel after all goroutines have finished is essential. This prevents further communication on the channel and allows for graceful resource management.

The provided code attempts to implement this behavior, but faces limitations due to race conditions. To address these challenges, we can utilize the sync.WaitGroup type.

The WaitGroup allows us to create a collection of tasks and wait for them to complete before continuing execution. In the context of closing a channel, we can use a WaitGroup to ensure that the channel is closed only when all goroutines have finished using it.

An improved code snippet using a WaitGroup:

import (
    "sync"
)

// ...

var wg sync.WaitGroup
for i := 0; i <= 10; i++ {
    wg.Add(1)
    go func() {
        result := calculate()
        c <- result
        wg.Done()
    }()
}

// Close the channel when all goroutines are finished
go func() {
    wg.Wait()
    close(c)
}()

for result := range c {
    all_result = append(all_result, result...)
}

In this updated code, we employ a WaitGroup to track the number of outstanding goroutines. Each goroutine executing the task increments the WaitGroup counter, indicating that it has started. Upon completion, each goroutine decrements the WaitGroup counter, indicating that it has finished. A separate goroutine waits on the WaitGroup and closes the channel once all goroutines have reported their completion.

This approach ensures a synchronized and reliable closing of the channel, preventing the issues encountered in the original code. It also eliminates the need for sleep calls and busy waiting, providing a more efficient and robust solution.

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