What Is New in Go 1.23

Go 1.23 introduces range-over-function iterators, allowing you to iterate over a function directly using the range keyword without creating an explicit iterator type. This feature simplifies code by letting you define iteration logic inline within a function that returns a channel or uses the new iter.Seq type.

func EvenNumbers(n int) iter.Seq[int] {
    return func(yield func(int) bool) {
        for i := 0; i < n; i++ {
            if i%2 == 0 && !yield(i) {
                return
            }
        }
    }
}

for num := range EvenNumbers(10) {
    fmt.Println(num)
}

Range-over-function iterators in Go 1.23 let you loop over a function just like you loop over a list, making your code cleaner and easier to read. Instead of writing complex helper classes to generate sequences, you can simply define a function that yields values one by one. Think of it as turning a recipe (the function) directly into a conveyor belt of ingredients (the values) for your loop to process.