Entity Relationship Error : UseLazyLoadingProxies requires all entity types to be public, unsealed, have virtual navigation properties, and have a pub

Hi All,
I trying to add an existing product id as a foreign key in my Entity.
I have created DiscountType class and added a property for products

public class DiscountType : BaseEntity 
    {
        public string TypeCode { get; set; }
        public string TypeName { get; set; }
    //Product is existing class of nop commerce
   public Product product { get; set; }
    }

Created DiscountTypeMap class and added relation between both tables

 public class DiscountTypeMap : NopEntityTypeConfiguration<DiscountType>
    {
       public override void Configure(EntityTypeBuilder<DiscountType > builder)
        {
            builder.ToTable(nameof(DiscountType ));
            builder.HasKey(point => point.Id);
            builder.HasOne<Product>(s => s.Product);
        } 
}

When running the plugin I am getting the following error

"Navigation property 'Addresses' on entity type 'Customer' is not virtual. UseLazyLoadingProxies requires all entity types to be public, unsealed, have virtual navigation properties, and have a public or protected constructor."

I am not sure why this error is coming.  Please share if I missed anything.

Thank You in advance.

Try making the Product property virtual in your DiscountType  class and see if it works