Closure in go

closure is a function inside another function where you can reference variable defined in the outer function.

I have seen them useful in dealing with packages where a function expects an type func() as an argument where the func() doesn’t take any argument.

example from package github.com/cenkalti/backoff

signature of backoff.Retry is as below

backoff.Retry(o backoff.Operation, b backoff.Backoff)

where backoff.Operation is of type func() error

type Operation func() error

func main() {
    func retryWrapper(imp string) func() error{
        return func() {
            funcThatCouldFail(imp)
            retun nil
        }
    }
    err := backoff.Retry(retryWrapper("hello world"), backoff.NewExponentialBackOff())
}

we can’t directly call funcThatCouldFail(imp) in backoff.Retry(). So, we create a wrapper which takes an argument and that argument is being used inside of the func that being returned.

• Go
• closure