Why Use Pointers and Variables with Go\'s WaitGroup?

WaitGroup Reference: Using Pointers and Variables

The WaitGroup in Go provides synchronization primitives for coordinating goroutines. It has three primary functions: Add, Done, and Wait. Here, we'll examine their usage and why they may be called using both pointers and variables.

WaitGroup Methods

As mentioned, all WaitGroup functions are called by a pointer to a WaitGroup, denoted by the *WaitGroup receiver type. This allows them to modify the internal state of the WaitGroup, tracking goroutine completion and waiting for them to finish.

Understanding Usage

The code snippet in question shows both pointer and variable usage for WaitGroup functions:

func main() {

    // Declared as a variable
    var wg sync.WaitGroup

    // Called with a pointer to the WaitGroup
    wg.Add(1)

    // Called with a variable (not a pointer)
    go worker(i, wg)
}

Passing a Pointer to the Worker

When passing the WaitGroup to the worker goroutine, it's crucial to pass its address using &. This is because the worker's Done function operates on the WaitGroup pointer, and passing it directly as a variable would create a copy, resulting in unexpected behavior.

Conclusion

In summary, all WaitGroup methods are designed to be called with a pointer receiver. Variables are used in the code snippet to simplify declaration and function calling. However, when passing the WaitGroup to goroutines, it's essential to pass its address (&) to ensure that all methods operate on the same underlying pointer.

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