Fibonacci closure with memorization in go

fibonacci.go

package main

import (
	"fmt"
	"math/big"
	"time"
)

func NewFibonacci() func(x int64) *big.Int {
	memo := make(map[int64]*big.Int)
	var fib func(x int64) *big.Int
	fib = func(x int64) *big.Int {
		n, exist := memo[x]
		if exist {
			return n
		} else {
			if x < 2 {
				memo[x] = big.NewInt(x)
			} else {
				memo[x] = new(big.Int)
				memo[x].Add(fib(x - 1), fib(x - 2))
			}
			return memo[x]
		}
	}
	return fib
}

func main() {
	start := time.Now()
	fib := NewFibonacci()
	limit := int64(1000)
	for i := int64(0); i <= limit; i++ {
		fmt.Println(i, ": ", fib(i))
	}
	elapsed := time.Since(start)
	fmt.Println("fibonacci elapsed time: ", elapsed)
}