8.go

package main

import (
	"fmt"
	"strconv"
	"strings"
)

func stringSequence(s string, w int, c chan []string) {
	digits := strings.Split(s, "")

	for i := range digits {
		if (i + w) > len(digits) {
			break
		}
		c <- digits[i : i+w]
	}
	close(c)
}

func main() {

	s := "73167176531330624919225119674426574742355349194934" +
		"96983520312774506326239578318016984801869478851843" +
		"85861560789112949495459501737958331952853208805511" +
		"12540698747158523863050715693290963295227443043557" +
		"66896648950445244523161731856403098711121722383113" +
		"62229893423380308135336276614282806444486645238749" +
		"30358907296290491560440772390713810515859307960866" +
		"70172427121883998797908792274921901699720888093776" +
		"65727333001053367881220235421809751254540594752243" +
		"52584907711670556013604839586446706324415722155397" +
		"53697817977846174064955149290862569321978468622482" +
		"83972241375657056057490261407972968652414535100474" +
		"82166370484403199890008895243450658541227588666881" +
		"16427171479924442928230863465674813919123162824586" +
		"17866458359124566529476545682848912883142607690042" +
		"24219022671055626321111109370544217506941658960408" +
		"07198403850962455444362981230987879927244284909188" +
		"84580156166097919133875499200524063689912560717606" +
		"05886116467109405077541002256983155200055935729725" +
		"71636269561882670428252483600823257530420752963450"

	w, max := 5, 0

	c := make(chan []string)

	go stringSequence(s, w, c)
	for da := range c {
		product := 1
		for _, ds := range da {
			d, _ := strconv.Atoi(ds)
			product *= d
		}
		if product > max {
			max = product
		}
	}
	fmt.Printf("Max product of a %d-character substring is %d.\n", w, max)
}