Not able to get delta results using a timestamp

Trying to achieve this using the sdk.

Sample Code:

func getDelta(ctx context.Context, client *msgraphsdkgo.GraphServiceClient, driveID, itemID string) error {
	reqHeaders := abstractions.NewRequestHeaders()
	reqHeaders.TryAdd("Prefer", "hierarchicalsharing, deltashowremovedasdeleted, deltatraversepermissiongaps, deltashowsharingchanges")

	timestamptoken := time.Now().UTC().Format(time.RFC3339)
        deltaResp, err := client.Drives().ByDriveId(driveID).Items().ByDriveItemId(itemID).DeltaWithToken(&timestamptoken).GetAsDeltaWithTokenGetResponse(ctx, &drives.ItemItemsItemDeltaWithTokenRequestBuilderGetRequestConfiguration{
		QueryParameters: &drives.ItemItemsItemDeltaWithTokenRequestBuilderGetQueryParameters{
			Select:[]string{"id", "name", "webUrl", "lastModifiedDateTime", "createdDateTime", "createdBy", "lastModifiedBy", "file", "size", "parentReference", "deleted", "shared"},
		},
		Headers: reqHeaders,
	})

	if err != nil {
		return err
	}

	fmt.Printf("deltaResp: %+v", deltaResp)
        return nil
}

But getting following error:

(400)[invalidRequest] Provided sync token is malformed, target:

I have tried following values for timestamptoken other than one mentioned in sample code:

1. url.QueryEscape(time.Now().UTC().Format(time.RFC3339))
2. "2021-09-29T20:00:00Z"

Start with the DeltaWithToken call in getDelta and compare its timestamp-token request with the linked Microsoft Graph delta example. Determine whether the Go SDK sends the timestamp as expected or whether the service rejects the supplied token; done means identifying a reproducible SDK fix or documenting that the request is unsupported or malformed.