Magento 2 Product Import – CSV Format for Size and Color Configurable Products

found the solution commented the below line in abstractype file in the model catalog product import. //$rowData = $productTypeModel->clearEmptyData($rowData);

hope this helps other anyone facing the same problem

You have to Follow below step for creating Configurable product.

1. Create Simple Product with require attribute.
2. Create Configurable Product with configurable_variations with contain SKU and attributes like sku=sku_of_simple_product,color=RED,size=XXSof Simple Product and one another column like configurable_variation_labels which contain color=Color,size=Size.
3. After perform this step you can import configurable product.

It may help you.