Toggle autoformat on save

[Nargonath]

Most of the time I enable autoformatting on save when I work on my own projects. However I do collaborate on other open-source projects that do not use my code style. When I write code there I want to disable the autoformat. I use the autocmd given in the Wiki and added a little twist to make it work, here is how it looks like:

local augroup = vim.api.nvim_create_augroup("LspFormatting", {})
vim.g.autoFormat = true

require("null-ls").setup({
    -- you can reuse a shared lspconfig on_attach callback here
    on_attach = function(client, bufnr)
        if client.supports_method("textDocument/formatting") then
            vim.api.nvim_clear_autocmds({ group = augroup, buffer = bufnr })
            vim.api.nvim_create_autocmd("BufWritePre", {
                group = augroup,
                buffer = bufnr,
                callback = function()
                    if vim.g.autoFormat then
                       vim.lsp.buf.format({ async = false })
                    end
                end,
            })
        end
    end,
})

Initially it works. Then I switch autoFormat to false with :lua vim.g.autoFormat=false for example. I make a modification in the code, hit :wand autoFormat is disabled properly. However if I enable it again it doesn't work. It's like my autocmd is not even triggered as I put a print() in the callback and it's not displayed. Is there something I'm missing here?