Function Closure in Go

Closure is a powerful concept in Go that allows you to define a function inside another function and use variables from the outer function within the inner function.

Here is a basic example of closure in Go:

func outerFunc() func() {
    count := 0 // variable to be used in inner function
    return func() {
        count++
        fmt.Println(count)
    }
}
func main() {

    innerFunc := outerFunc()
innerFunc() // prints 1

    innerFunc() // prints 2

    innerFunc() // prints 3

}

In the example above, outerFunc returns another function that increments the count variable and then prints its value. The main function creates a closure of outerFunc and assigns the returned function to the variable innerFunc. When innerFunc is called, it uses the count variable from outerFunc and increments it with each call.

Another example of closure in Go is when you want to create a function with some pre-loaded data. Here's how to build that closure:

func generateMessage(name string) func() string {
    return func() string {
        return "Hello " + name + "!"
    }
}
func main() {

    messageFunc := generateMessage("John")

    fmt.Println(messageFunc()) // prints "Hello John!"
messageFunc = generateMessage("Jane")

    fmt.Println(messageFunc()) // prints "Hello Jane!"
}

In this example, the generateMessage function takes in a name parameter and returns another function that concatenates the name parameter with a greeting message. The closure allows you to reuse the returned function multiple times with different names.

Closure is a powerful concept that can be used in many scenarios. It can simplify your code and make it more readable.