Coroutines for Timed Sequences

using System.Collections;
using UnityEngine;

public class DoorController : MonoBehaviour
{
    public void Open() => StartCoroutine(OpenSequence());

    private IEnumerator OpenSequence()
    {
        PlayCreakSound();
        yield return new WaitForSeconds(0.3f);

        float t = 0;
        Quaternion closed = transform.rotation;
        Quaternion open   = closed * Quaternion.Euler(0, 90, 0);

        while (t < 1f)
        {
            t += Time.deltaTime * 2f;
            transform.rotation = Quaternion.Slerp(closed, open, t);
            yield return null;  // wait one frame
        }
    }
}