Where can I get the SourceToken for the customer creation in Stripe?

Here is the example of the code which uses the SourceToken:

if (Request.Form["stripeToken"] != null) {
    var customers = new CustomerService();
    var charges = new ChargeService();

    var customer = customers.Create(new CustomerCreateOptions {
        Email = Request.Form["stripeEmail"],
        SourceToken = Request.Form["stripeToken"]
    });

    var charge = charges.Create(new ChargeCreateOptions {
        Amount = 500,
        Description = "Sample Charge",
        Currency = "usd",
        CustomerId = customer.Id
    });

    Console.WriteLine(charge);
}

What is SourceToken out of this json?

{
  "id": "tok_1EL43MKfPgrABB02rh7IGG7l",
  "object": "token",
  "card": {
    "id": "card_1EL43MKfPgrABB02yFgReMXc",
    "object": "card",
    "address_city": null,
    "address_country": null,
    "address_line1": null,
    "address_line1_check": null,
    "address_line2": null,
    "address_state": null,
    "address_zip": null,
    "address_zip_check": null,
    "brand": "Visa",
    "country": "US",
    "cvc_check": "pass",
    "dynamic_last4": null,
    "exp_month": 12,
    "exp_year": 2020,
    "funding": "credit",
    "last4": "4242",
    "metadata": {},
    "name": "foo@gmail.com",
    "tokenization_method": null
  },
  "client_ip": "194.44.142.6",
  "created": 1554278556,
  "email": "foo@gmail.com",
  "livemode": false,
  "type": "card",
  "used": false
}

Here is how I got the json:

var stripe = Stripe('pk_test_ob6s7KZxZU1mouJbbsuFBjEe');

var handler = StripeCheckout.configure({
    key: 'pk_test_ob6s7KZxZU1mouJbbsuFBjEe',
    token: function(token, args) {
        var stop = 0;
    }
  });

  document.getElementById('myBtn').addEventListener('click', function(e) {
    // Open Checkout with further options
    handler.open({
      name: 'Demo Site',
      description: '2 widgets ($20.00)',
      amount: 2000
    });
    e.preventDefault();
  });

on line var stop = 0;.

The example is taken from here.

Solution

The SourceToken in that JSON is "tok_1EL43MKfPgrABB02rh7IGG7l".

After the customer is created with the source attached (e.g. that token), you can retrieve the customer which will include that customer's sources (they'll be listed in the sources object under the customer record).

The token itself gets consumed during the creation of the source and customer, and the result is a source that's reusable.