Added Go implementation

Go/xor.go

@@ -0,0 +1,11 @@
+package xor
+
+// EncryptDecrypt runs a XOR encryption on the input string, encrypting it if it hasn't already been,
+// and decrypting it if it has, using the key provided.
+func EncryptDecrypt(input, key string) (output string) {
+	for i := range input {
+		output += string(input[i] ^ key[i%len(key)])
+	}
+
+	return output
+}

Go/xor_test.go

@@ -0,0 +1,22 @@
+package xor
+
+import "testing"
+
+func TestEncryptDecrypt(t *testing.T) {
+	sample := "kylewbanks.com"
+	key := "KCQ"
+
+	// Test encrypting
+	encrypted := EncryptDecrypt(sample, key)
+	if encrypted == sample {
+		t.Fatalf("Expected encrypted string not to match the input: %v", encrypted)
+	} else if len(encrypted) != len(sample) {
+		t.Fatalf("Expected encrypted string to have the same length as the input: %v", len(encrypted))
+	}
+
+	// Test decrypting
+	decrypted := EncryptDecrypt(encrypted, key)
+	if decrypted != sample {
+		t.Fatalf("Expected decrypted string to match the original input: %v", decrypted)
+	}
+}