Explain the use of Go's closure for encapsulating variables in a function?

A closure is a function value that references variables from outside its body. In Go, a closure is created by defining a function that captures and references one or more variables defined outside the function. These captured variables are then available to the closure even after the function that created it has returned.

Here is an example of a closure in Go:

func adder(x int) func(int) int {
    return func(y int) int {
        return x + y
    }
}

func main() {
    add := adder(10)
    fmt.Println(add(5)) // output: 15
    fmt.Println(add(10)) // output: 20
}

In this example, the **adder** function returns a closure that adds the argument passed to it with the **x** value captured from the **adder** function. When **adder** is called with an argument of 10, it returns a closure that adds 10 to its argument. This closure is assigned to the **add** variable, which is then used to add 5 and 10 to 10 respectively. The **x** value captured by the closure remains available to it even after **adder** has returned.

Closures are often used in Go for encapsulating variables and creating functions that behave like objects. They can be used to implement a variety of programming patterns, such as decorators, iterators, and callbacks.