go: add «1071. Greatest Common Divisor of Strings»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/greatest-common-divisor-of-strings.go

@@ -0,0 +1,17 @@
+package main
+
+func gcdOfStrings(str1 string, str2 string) string {
+	gcd := func(x, y int) int {
+		for y != 0 {
+			x, y = y, x%y
+		}
+		return x
+	}
+
+	if str1+str2 != str2+str1 {
+		return ""
+	}
+
+	length := gcd(len(str1), len(str2))
+	return str1[:length]
+}