How to write in tinygo bluetooth with response?

Question

I'm trying to use Tinygo Bluetooth to connect to a Timeflip v2 (https://github.com/DI-GROUP/TimeFlip.Docs/blob/master/Hardware/TimeFlip%20BLE%20protocol%20ver4_02.06.2020.md).
The API documentation says, that I need to login (which is a write to f1196f57-71a4-11e6-bdf4-0800200c9a66, followed by a read on f1196f53-71a4-11e6-bdf4-0800200c9a66 for checking the result of the login).
The only thing I see in TinyGo for DeviceCharacteristics is WriteWithoutResponse (https://pkg.go.dev/github.com/tinygo-org/bluetooth#DeviceCharacteristic.WriteWithoutResponse).
When I use this, it looks like having no affect on the result.

package main

import (
    "log"
    "strconv"
    "tinygo.org/x/bluetooth"
)

var adapter = bluetooth.DefaultAdapter

const (
    timeFlipService          = "f1196f50-71a4-11e6-bdf4-0800200c9a66"
    commandOutCharacteristic = "f1196f53-71a4-11e6-bdf4-0800200c9a66"
    passwordCharacteristic   = "f1196f57-71a4-11e6-bdf4-0800200c9a66"
)

func main() {
    if err := adapter.Enable(); err != nil {
        log.Fatalln(err)
    }

    ch := make(chan bluetooth.ScanResult, 1)
    log.Println("scanning...")
    if err := adapter.Scan(func(adapter *bluetooth.Adapter, device bluetooth.ScanResult) {
        log.Println(device)
        if device.LocalName() == "TimeFlip v2.0" {
            log.Println("found timeflip")
            if err := adapter.StopScan(); err != nil {
                log.Println(err)
            }
            ch <- device
        }
    }); err != nil {
        log.Fatalln(err)
    }

    var device *bluetooth.Device
    select {
    case result := <-ch:
        var err error
        device, err = adapter.Connect(result.Address, bluetooth.ConnectionParams{})
        if err != nil {
            log.Fatalln(err)
        }
        log.Println("connected to ", result.Address.String())
    }
    defer func() {
        if err := device.Disconnect(); err != nil {
            log.Println(err)
        } else {
            log.Println("disconnected")
        }
    }()

    tfService, _ := bluetooth.ParseUUID(timeFlipService)
    srvcs, err := device.DiscoverServices([]bluetooth.UUID{tfService})
    if err != nil {
        log.Fatalln(err)
    }

    buf := make([]byte, 20)

    password, _ := bluetooth.ParseUUID(passwordCharacteristic)
    cmdOut, _ := bluetooth.ParseUUID(commandOutCharacteristic)
    for _, srvc := range srvcs {
        log.Println("- service", srvc.UUID().String())

        chars, err := srvc.DiscoverCharacteristics([]bluetooth.UUID{password, cmdOut})
        if err != nil {
            log.Println(err)
        }

        var pwChar bluetooth.DeviceCharacteristic
        var cmdOutChar bluetooth.DeviceCharacteristic

        for _, char := range chars {
            log.Println("-- characteristic", char.UUID().String())
            switch char.UUID() {
            case password:
                pwChar = char
            case cmdOut:
                cmdOutChar = char
            }

        }
        rightPassword := []byte{0x30, 0x30, 0x30, 0x30, 0x30, 0x30}
        _, err = pwChar.WriteWithoutResponse(rightPassword)
        if err != nil {
            log.Println("    ", err.Error())
        }
        n, err := cmdOutChar.Read(buf)
        if err != nil {
            log.Println("    ", err.Error())
        } else {
            log.Println("    data bytes", strconv.Itoa(n))
            log.Println("    value =", buf[:n])
        }
        wrongPassword := []byte{0x30, 0x30, 0x30, 0x30, 0x30, 0x31}
        _, err = pwChar.WriteWithoutResponse(wrongPassword)
        if err != nil {
            log.Println("    ", err.Error())
        }
        n, err = cmdOutChar.Read(buf)
        if err != nil {
            log.Println("    ", err.Error())
        } else {
            log.Println("    data bytes", strconv.Itoa(n))
            log.Println("    value =", buf[:n])
        }
    }

}

results in

scanning...
{7A:05:BF:06:97:D6 -61 0xc00029c1e0}
{C6:D8:C0:F7:A7:3C -57 0xc00029c480}
found timeflip
connected to  C6:D8:C0:F7:A7:3C
- service f1196f50-71a4-11e6-bdf4-0800200c9a66
-- characteristic f1196f57-71a4-11e6-bdf4-0800200c9a66
-- characteristic f1196f53-71a4-11e6-bdf4-0800200c9a66
    data bytes 1
    value = [1]
    data bytes 1
    value = [1]
disconnected

At least one of the results should be 0x02 (invalid password).

Could somebody give me a hint?