IEnumerator MoveOverDistance()
{
    direction = (transform.position - startPosition).normalized;

    float currentDistance = 0f;
    float distance = //jusqu'à l'infinie et au delà
    while (currentDistance < distance)
    {
        float step = speed * Time.deltaTime;

        transform.position += direction * step;

        currentDistance = Vector3.Distance(startPos, transform.position);

        yield return null;
    }

    transform.position = startPos + direction * distance;
}