func main() {
    client := horizonclient.DefaultPublicNetClient
    opRequest := horizonclient.OperationRequest{Cursor: "now"}

    ctx, _ := context.WithCancel(context.Background())

    printHandler := func(op operations.Operation) {
        go func() {
            // Do something here
        }()
    }
    err := client.StreamPayments(ctx, opRequest, printHandler)
    if err != nil {
        fmt.Println(err)
    }
}