code: func makeHA2(auth *authorization, method, uri string) string {
  	A2 := fmt.Sprintf("%s:%s", method, uri)
  	return hash([]byte(A2), auth.algorithm)
  }
docs: // makeHA2 returns the HA2 hash, where
  //
  //     HA2 = H(A2) = H(method:digestURI)
  //
  // and H is one of MD5 or SHA256.