How do I iterate over the paginated list returned by Google Admin SDK UsersService.List?

So I am reading a paginated list of users successfully from the Admin API. I can see the NextPageToken as well as the first page of results. But there seems to be nothing in the returned UsersListCall object for me to iterate over? No place to specify the next page token, as we'd do with the HTTP style calls. Can someone give me a hint on where to start to iterate through these pages?

    adminService, err := admin.NewService(ctx,
        option.WithCredentials(credentials),
    )
    [...]
    users, err := adminService.Users.List().Customer("my_customer").Do()
    if err != nil {
        if e, ok := err.(*googleapi.Error); ok {
            fmt.Printf("Error code: %v\n", e.Code)
            fmt.Printf("Message: %v\n", e.Message)
        } else {
            fmt.Printf("Error: %v\n", err)
        }
        os.Exit(1)
    }

    fmt.Printf("token: %s\n", users.NextPageToken)

    for _, user := range users.Users {
        fmt.Printf("User: %s (%s)\n", user.Name.FullName, user.PrimaryEmail)
    }

The "trick" is to create an initial request and then use it to page with the response's NextPageToken until there are no more tokens.

Try:

package main

import (
    "context"
    "fmt"
    "os"

    admin "google.golang.org/api/admin/directory/v1"
    "google.golang.org/api/googleapi"
)

func main() {
    ctx := context.Background()
    adminService, err := admin.NewService(ctx)
    if err != nil {
        panic(err)
    }


    // Create a request
    rqst := adminService.Users.List().Customer("my_customer")
    // Loop
    for {
        // Do'ing the request
        resp, err := rqst.Do()
        if err != nil {
            if e, ok := err.(*googleapi.Error); ok {
                fmt.Printf("Error code: %v\n", e.Code)
                fmt.Printf("Message: %v\n", e.Message)
            } else {
                fmt.Printf("Error: %v\n", err)
            }
            os.Exit(1)
        }

        for _, user := range resp.Users {
            fmt.Printf("User: %s (%s)\n", user.Name.FullName, user.PrimaryEmail)
        }

        // Until there aren't any more pages
        if resp.NextPageToken == "" {
            break
        }

        // Using the NextPageToken to page
        rqst.PageToken(resp.NextPageToken)
    }
}