Simple retry mechanism with delay and backoff

retry.go

package main

import (
  "time"
  "fmt"
)

func pow(a, b int) int {
	p := 1
	for b > 0 {
		if b&1 != 0 {
			p *= a
		}
		b >>= 1
		a *= a
	}
	return p
}

func pow2(a int) int {
	return pow(a, 2)
}

func retry(fn func(int) int) func() int {
	var attempt int
	return func() int {
		time.Sleep(time.Duration(fn(attempt)) * time.Second)
		attempt++
		return attempt
	}
}

func main() {
  for r := retry(pow2); r() <= 3; {
    fmt.Println("attempt")
  }
}