Recursion

Go supports recursive functions. Here’s a classic example.

package main

import "fmt"

// This fact function calls itself
// until it reaches the base case of fact(0).
func fact(n int) int {
    if n == 0 {
        return 1
    }
    return n * fact(n-1)
}

func main() {
    fmt.Println(fact(7))

    // Closures can also be recursive
    // but this requires the closure to be declared
    // with a typed var explicitly before it’s defined.
    var fib func(n int) int

    fib = func(n int) int {
        if n < 2 {
            return n
        }

        // Since fib was previously declared in main
        // Go knows which function to call with fib here.
        return fib(n-1) + fib(n-2)
    }

    fmt.Println(fib(7))
}

$ go run recursion.go
5040
13