adding go code for calculating gcd (#1052)

Author: rmoreira

gcd/go/gcd.go

@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func gcd(a, b int) int {
+	if b == 0 {
+		return a
+	} else {
+		return gcd(b, a%b)
+	}
+}
+
+func main() {
+	fmt.Println("Please provide 2 numbers")
+	fmt.Print("First number: ")
+	var a int
+	fmt.Scan(&a)
+	fmt.Print("Second number: ")
+	var b int
+	fmt.Scan(&b)
+	fmt.Printf("gcd(%d,%d)=%d\n", a, b, gcd(a, b))
+}