Add Golang example

[SevereCloud]

valid_test.go полностью покрывающий isValid

[dvmazur]

The function is not working correctly. You forgot to encode the URL before feeding it to HMAC. I suggest you change the _, _ = mac.Write([]byte(strings.Join(vkParams, "&"))) line to _, _ = mac.Write([]byte(url.PathEscape(strings.Join(vkParams, "&")))).