I have a Github App on Github Enterprise 2.17. When I try to create an access token for my App using the JWT  for the first 4 or 5 seconds, it is rejected by the server with the error:

401 - ‘Issued at’ claim (‘iat’) must be an Integer representing the time that the assertion was issued // See: https://developer.github.com/enterprise/2.17/v3
After 4 seconds pass and several retries server accepts the JWT and returns an access token

I have a script demonstrating the behavior:

require 'json'
require 'openssl'
require 'octokit'
require 'jwt'
require 'time'
require 'pp'
require 'pry'
Octokit.configure do |c|

c.api_endpoint = 'https://mygithubserver.com/api/v3/'

end
GITHUB_APP_ID = 2

GITHUB_APP_PRIVATE_KEY_FILE = 'github.app.pem'.freeze

GITHUB_INSTALLATION_ID = 4
payload = {

iat: Time.now.to_i,

exp: Time.now.to_i + (9 * 60),

iss: GITHUB_APP_ID

}
Cryptographically sign the JWT
private_pem = File.read(GITHUB_APP_PRIVATE_KEY_FILE)

private_key = OpenSSL::PKey::RSA.new(private_pem)

jwt = JWT.encode(payload, private_key, 'RS256')
client = Octokit::Client.new(bearer_token: jwt)
begin

installation_token = client.create_app_installation_access_token(GITHUB_INSTALLATION_ID, accept: 'application/vnd.github.machine-man-preview+json')[:token]

rescue Octokit::Unauthorized => e

puts "ERROR: #{e}"

sleep(1)

retry

end

Is this the expected behavior?