How Does Go Handle Variable Sharing Between Goroutines?

Go's Approach to Variable Sharing in Goroutines

Concurrency is an essential aspect of Golang, and understanding how variables are shared between goroutines is crucial. Let's explore this concept through an example and delve into how Go's runtime manages variable access.

Consider the following code snippet:

<code class="go">for i := 0; i < 5; i++ {
    go func() {
        fmt.Println(x) // Line X1
    }()
}</code>

In this code, a loop is used to create multiple goroutines. Each goroutine attempts to access the x variable defined outside the loop (Line X1). When executed, this code prints the values 4, 0, 1, 3, 2 in random order.

Now, let's modify the code slightly:

<code class="go">for i := 0; i < 5; i++ {
    go func() {
        fmt.Println(i) // Line X2
    }()
}</code>

In this case, each goroutine accesses the i variable within the loop (Line X2). When executed, this code prints 5, 5, 5, 5, 5, indicating a significant difference from the previous result.

To understand the disparity, it's important to note that in the first example, a new x variable is created within each goroutine due to variable shadowing. As a result, each goroutine has its own unique x variable, leading to the random print order.

In the second example, however, the i variable is used directly within the goroutine, avoiding variable shadowing. Therefore, all goroutines access the same i variable, resulting in the uniform print value of 5.

This behavior highlights a key difference in Go's handling of variables between goroutines. While variable shadowing can provide isolation, it can also lead to unexpected results. By understanding this concept and utilizing appropriate techniques such as passing values into goroutines, developers can prevent data races and ensure proper variable sharing in their Golang applications.

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