Modify drop of shulker box

I have a server with friends on vanilla 1.13.2 and I am trying to change the drop of the shulker box. I want that always drop 2 shulker shells but I can't make that they drop correctly.

I tried puting a shulker.JSON in data/loot_tables/minecraft/entities but nothing happend.

the content of the .JSON was:

{
"pools": [
    {
        "rolls": 1,
        "entries": [
            {
                "type": "item",
                "name": "minecraft:shulker_shell",
                "weight": 1,
                "functions": [
                    {
                        "function": "set_count",
                        "count": 2
                    }
                ]
            }
        ]
    }
]
}

Your loot file needs to be at somedatapack/data/minecraft/loot_tables/entities/shulker.json, not somedatapack/data/loot_tables/minecraft/entities. Here's the double shulker shell loot file I use:

{
  "pools": [
    {
      "rolls": 2,
      "entries": [
        {
          "type": "minecraft:item",
          "name": "minecraft:shulker_shell"
        }
      ]
    }
  ]
}

If it still doesn't work, try renaming it to shulker.json instead of shulker.JSON. I'm not sure if it's case-sensitive.