Gem::GemcutterUtilities#fetch_otp

# File tmp/rubies/ruby-3.3.0/lib/rubygems/gemcutter_utilities.rb, line 255
def fetch_otp(credentials)
  options[:otp] = if webauthn_url = webauthn_verification_url(credentials)
    server = TCPServer.new 0
    port = server.addr[1].to_s

    url_with_port = "#{webauthn_url}?port=#{port}"
    say "You have enabled multi-factor authentication. Please visit #{url_with_port} to authenticate via security device. If you can't verify using WebAuthn but have OTP enabled, you can re-run the gem signin command with the `--otp [your_code]` option."

    threads = [WebauthnListener.listener_thread(host, server), WebauthnPoller.poll_thread(options, host, webauthn_url, credentials)]
    otp_thread = wait_for_otp_thread(*threads)

    threads.each(&:join)

    if error = otp_thread[:error]
      alert_error error.message
      terminate_interaction(1)
    end

    say "You are verified with a security device. You may close the browser window."
    otp_thread[:otp]
  else
    say "You have enabled multi-factor authentication. Please enter OTP code."
    ask "Code: "
  end
end