suspendAsync2.kt

suspend fun saveUsernameAndPassword(username: String, password: String) {

    val result = suspendAsync(StorageService.getInstance()::saveUsernameAndPassword, username, password)
    handleResult(result)
}

suspend fun <Input1, Input2, Output> suspendAsync(function: (Input1, Input2, (Output) -> Unit) -> Unit,
                                                  inputOne: Input1, inputTwo: Input2) =  suspendCoroutine<Output> { continuation ->
    function(inputOne, inputTwo) { output ->
        continuation.resume(output)
    }
}