IEnumerator Start()
{
    var rt = new RenderTexture(512, 512, 0);
    //Graphics.xxx...
    var req = AsyncGPUReadback.Request(rt);
    yield return new WaitUntil(() => req.done);

    var tex = new Texture2D(512, 512, TextureFormat.RGBA32, false);
    var colorArray = req.GetData<Color32>().ToArray();
    tex.SetPixels32(colorArray);
    tex.Apply();
}

RenderTexture.active = rt;
var tex = new Texture2D(512, 512, TextureFormat.RGBA32, false);
tex.ReadPixels(new Rect(0, 0, 512, 512), 0, 0, false);
tex.Apply();

#pragma kernel CSMain

struct TestData
{
    float3 pos;
};
RWStructuredBuffer<TestData> MyData;

[numthreads(8,1,1)]
void CSMain (uint3 id : SV_DispatchThreadID)
{
    MyData[id.x].pos = MyData[id.x].pos * 2;
}

public class ComputeShaderAsyncRequest : MonoBehaviour
{
    public struct TestData
    {
        public Vector3 pos;
    }
    public ComputeShader computeShader;

    IEnumerator Start()
    {
        var kernelID = computeShader.FindKernel("CSMain");

        var testData = new List<TestData>();
        for (int i = 0; i < 64; i++)
            testData.Add(new TestData() { pos = new Vector3(i, 0, 0) });

        var computeBuffer = new ComputeBuffer(testData.Count, 12);
        computeBuffer.SetData(testData);
        computeShader.SetBuffer(kernelID, "MyData", computeBuffer);
        computeShader.Dispatch(kernelID, 8, 1, 1);
        var request = AsyncGPUReadback.Request(computeBuffer);
        Debug.Log("frame1: " + Time.frameCount);//1
        yield return new WaitUntil(() => request.done);
        Debug.Log("frame2: " + Time.frameCount);//4

        var testDataArray = request.GetData<TestData>().ToArray();
        for (int i = 0; i < testDataArray.Length; i++)
            Debug.Log("i :" + i + "item: " + testDataArray[i].pos);
    }
}

public class ComputeShaderAsyncRequest_Sync : MonoBehaviour
{
    public struct TestData
    {
        public Vector3 pos;
    }

    public ComputeShader computeShader;

    void Start()
    {
        var kernelID = computeShader.FindKernel("CSMain");

        var testData = new List<TestData>();
        for (int i = 0; i < 64; i++)
            testData.Add(new TestData() { pos = new Vector3(i, 0, 0) });

        var computeBuffer = new ComputeBuffer(testData.Count, 12);
        computeBuffer.SetData(testData);
        computeShader.SetBuffer(kernelID, "MyData", computeBuffer);
        computeShader.Dispatch(kernelID, 8, 1, 1);
        var array = new TestData[testData.Count];
        computeBuffer.GetData(array);
        for (int i = 0; i < array.Length; i++)
            Debug.Log("i :" + i + "item: " + array[i].pos);
    }
}