Please provide reference

[ndenisj]

I keep getting 'please provide reference' when trying to test bank payment

void _processPayment() {
    try {
      PaystackPayManager(context: context)
        // Don't store your secret key on users device.
        // Make sure this is retrive from your server at run time
        // ..setSecretKey("")
        ..setSecretKey("sk_test_435a0cd0d7fbc14531713064c764ed2e644d3efe")
        //accepts widget
        ..setCompanyAssetImage(Image(
          image: AssetImage("assets/images/logo.png"),
        ))
        ..setAmount(1000 * 100)
        // ..setReference("your-unique-transaction-reference")
        ..setReference(DateTime.now().millisecondsSinceEpoch.toString())
        ..setCurrency("NGN")
        ..setEmail("bakoambrose@gmail.com")
        ..setFirstName("Ambrose")
        ..setLastName("Bako")
        ..setMetadata(
          {
            "custom_fields": [
              {
                "value": "snapTask",
                "display_name": "Payment to",
                "variable_name": "payment_to"
              }
            ]
          },
        )
        ..onSuccesful(_onPaymentSuccessful)
        ..onPending(_onPaymentPending)
        ..onFailed(_onPaymentFailed)
        ..onCancel(_onPaymentCancelled)
        ..initialize();
    } catch (error) {
      print("Payment Error ==> $error");
    }
  }