code: func Sign(authKeys Auth, r *http.Request) error {
  	sv := new(Service)
  	if awsKinesisRegexp.MatchString(r.Host) {
  		parts := strings.Split(r.Host, ".")
  		sv.Name = parts[0]
  		sv.Region = parts[1]
  	}
  	return sv.Sign(authKeys, r)
  }
docs: // Sign signs a request with a Service derived from r.Host