class Google::Cloud::Env::ComputeMetadata

def identity_token_lifetime data
  return 0 unless data =~ /^[\w=-]+\.([\w=-]+)\.[\w=-]+$/
  base64 = Base64.urlsafe_decode64 Regexp.last_match[1]
  json = JSON.parse base64 rescue nil
  return 0 unless json.respond_to?(:key?) && json&.key?("exp")
  lifetime = json["exp"].to_i - Time.now.to_i - TOKEN_EXPIRY_BUFFER
  lifetime = 0 if lifetime.negative?
  lifetime
end