Hands-On Full Stack Development with Go

Closures

A function can also be a closure. A closure is a function value that's bound to variables outside its body. This means that a closure can access and change values on those variables. It is hard to understand closures without an example. Here is another flavor of the adder function, which returns a closure:

func adder() func(int) int {  sum := 0  return func(x int) int {    sum += x    return sum  }}

The closure in the preceding example has access to the sum variable, which means that it will remember the current value of the sum variable, and will also be able to change the value of the sum variable. Again, this is best explained with another example:

func adder() func(int) int {  sum := 0  return func(x int) int {    sum += x    return sum  }}func ...