Implemented GCD in Go (#5025)

* Added GCD in Go

* Updated README.md

Author: nidh-ish

Go/README.md

@@ -50,6 +50,7 @@
 - [Ugly Number](math/Ugly_Number)
 - [Fibonacci Number](math/Fibonacci)
 - [Mystery Number](math/Mystery_Number)
+- [GCD](math/GCD)
 
 ## Others
 - [Tower of Hanoi](other/tower_of_hanoi)

Go/math/GCD/GCD.go

@@ -0,0 +1,58 @@
+/* This program calculates the GCD(Greatest Common Divisor)
+of two numbers given as input.*/
+
+package main
+
+import (
+	"fmt"
+)
+
+// This function finds the minimum of two numbers and returns it
+func min(n1, n2 int) int {
+	if(n1 < n2) {
+		return n1
+	} else {
+		return n2
+	}
+}
+
+// This function calculates the GCD.
+func is_gcd(n1, n2 int) int {
+
+	// Find the minimum of two numbers
+	var min int = min(n1, n2)
+	var result int
+
+	// Iterate till the minimum
+	for i := 1; i <= min; i++ {
+		// It it divides both n1 and n2
+		if(n1 % i == 0 && n2 % i == 0) {
+			// Set it as gcd
+			result = i
+		}
+	}
+	// After completion return the GCD
+	return result
+}
+
+func main() {
+
+	// Take two numbers as input from the user
+	fmt.Print("Enter two numbers followed by spaces: ")
+	var n1, n2 int
+	fmt.Scan(&n1, &n2)
+
+	// Call the GCD function
+	var result int = is_gcd(n1, n2)
+
+	// Print the result
+	fmt.Print("\nGCD of ", n1, " and ", n2, " is ", result, "\n")
+}
+
+/* Sample I/O:
+
+Enter two numbers followed by spaces: 100 12
+
+GCD of 100 and 12 is 4
+
+*/