Code to find the Greatest Common Divisor (GCD) of 2 or more numbers.

FindGCD.go

package main

import "fmt"

// PrimeGenerator creates a generator goroutine that returns prime numbers, least first
func PrimeGenerator(close <-chan int) chan int {
	var current int
	var flag bool
	ch := make(chan int)

	go func() {
		current = 1
		for {
			select {
			case <-close:
				// When channel is closed, i.e., requested for closure
				return

			default:
				if current < 3 {
					// For prime numbers 2 & 3
					current++
					ch <- current
				} else {
					// For Prime Numbers greater than 3
					for i := current + 1; ; i++ {
						flag = true
						for j := 2; j <= i/2; j++ {
							if i%j == 0 {
								flag = false
								break
							}
						}

						// When the number is not perfectly divisible by any number except 1 & itself.
						if flag {
							ch <- i
							current = i
							break
						}
					}
				}
			}
		}
	}()

	return ch
}

// allGreaterThanOrEqual iterates over slice to check all elements are greater than given number
func allGreaterThanOrEqual(arr []int, n int) bool {
	for _, a := range arr {
		if a < n {
			return false
		}
	}
	return true
}

// allPerfectlyDivisible iterates over slice to check all elements are divisible by given number
func allPerfectlyDivisible(arr []int, n int) bool {
	for _, a := range arr {
		if a%n != 0 {
			return false
		}
	}
	return true
}

// divideFromAll iterates over slice to divide all elements by given number
func divideFromAll(arr []int, n int) []int {
	var result []int
	for _, a := range arr {
		a /= n
		result = append(result, a)
	}
	return result
}

// findGCD returns Greatest Common Divisor (GCD) of given slice of numbers
func findGCD(nums ...int) int {
	var p, gcd int

	// Generator for prime numbers
	closeCh := make(chan int)
	defer close(closeCh)
	ch := PrimeGenerator(closeCh)

	gcd = 1
	p = <-ch
	for allGreaterThanOrEqual(nums, p) {
		// When all numbers are greater than prime number p
		for allPerfectlyDivisible(nums, p) {
			// When all numbers are perfectly divisible by prime number p
			// Iterate to see if same prime number can divide multiple times
			gcd *= p

			// Divide prime number p from all the numbers
			nums = divideFromAll(nums, p)
		}

		// Read higher prime number for next iteration
		p = <-ch
	}
	return gcd
}

func main() {
	fmt.Println(findGCD(54, 90, 180, 720, 3600))
}