Keybindings defined in lsp on_attach do not load whichkey

[sandorex]

Here's the issue, i have keybindings that i define in on_attach function of LSP server in nvim-lspconfig, and the keys defined here do not start whichkey at all until i press leader or [ to start some other keybindings sequence

which-key is loaded like so in another file

    {
        'folke/which-key.nvim',
        event = 'VeryLazy',
        opts = {},
    },

lua/plugins/lsp.lua:

-- lazy.vim configuration for lsp, for server configs go to core.lsp_configs

local function on_attach()
    -- TODO add keybindings for listing all diagnostics in whole file, all buffers etc
    -- TODO add global function for creating toggle functions and binding keys to them
    -- add toggle for floating diagnostics
    local group_name = 'core_float_diagnostics'
    local set_floating_diagnostics = function(value)
        if value == nil then
            value = not vim.b.float_diagnostics_enabled
        end

        local group = vim.api.nvim_create_augroup(group_name, { clear = true })
        if value then
            vim.api.nvim_create_autocmd('CursorHold', {
                desc = 'Open diagnostics floating window automatically',
                group = group,
                callback = function()
                    vim.diagnostic.open_float(nil, { focus = false })
                end
            })
        end

        vim.b.float_diagnostics_enabled = value
    end

    -- default to true
    set_floating_diagnostics(true)

    -- toggles
    vim.keymap.set({ 'n' }, '<F2>f', function() set_floating_diagnostics(nil) end, { desc = 'Toggle between floating and inline diagnostics', buffer = true, silent = true })

    -- other
    vim.keymap.set({ 'n', 'v' }, '<F3>f', vim.lsp.buf.format, { desc = 'Format selection or whole buffer' })
end

return {
    {
        'neovim/nvim-lspconfig',
        lazy = false,
        dependencies = {
            'williamboman/mason.nvim',
            'williamboman/mason-lspconfig.nvim',

            -- adds neovim api completion
            'folke/neodev.nvim',

            -- autocompletion and snippets
            'hrsh7th/nvim-cmp',
            'hrsh7th/cmp-nvim-lsp',
            'L3MON4D3/LuaSnip',
            'saadparwaiz1/cmp_luasnip',
        },
        config = function()
            -- has to be loaded before lspconfig
            require('neodev').setup {}

            local capabilities = vim.lsp.protocol.make_client_capabilities()
            capabilities = require('cmp_nvim_lsp').default_capabilities(capabilities)

            require('mason').setup()
            local mason_lspconfig = require('mason-lspconfig')

            -- load configs from separate file
            local configs = require('core.lspconfig');

            -- used on all servers
            local default_server_config = {
                capabilities = capabilities,
                on_attach = on_attach,
            }

            -- autoconfigure servers
            mason_lspconfig.setup(configs.configs.mason_lsp)
            mason_lspconfig.setup_handlers {
                function(server_name)
                    require('lspconfig')[server_name].setup(vim.tbl_extend('force', default_server_config, configs.configs[server_name]))
                end,
            }

            -- autocompletion setup
            local cmp = require 'cmp'
            local luasnip = require 'luasnip'

            luasnip.config.setup {}

            -- load snippets lazily
            require("luasnip.loaders.from_snipmate").lazy_load()
            require("luasnip.loaders.from_lua").lazy_load({ paths = "~/.config/nvim/LuaSnip/" })

            cmp.setup {
                snippet = {
                    expand = function(args)
                        luasnip.lsp_expand(args.body)
                    end,
                },
                -- i changed many things so it does not automatically focus
                mapping = cmp.mapping {
                    ['<S-Down>'] = {
                        i = cmp.mapping.select_next_item {
                            behavior = cmp.SelectBehavior.Select
                        },
                    },
                    ['<S-Up>'] = {
                        i = cmp.mapping.select_prev_item {
                            behavior = cmp.SelectBehavior.Select
                        },
                    },
                    ['<C-d>'] = cmp.mapping.scroll_docs(-4),
                    ['<C-f>'] = cmp.mapping.scroll_docs(4),
                    ['<C-Space>'] = cmp.mapping.complete {},
                    ['<CR>'] = cmp.mapping.confirm {
                        behavior = cmp.ConfirmBehavior.Replace,
                        select = false,
                    },
                    -- the suggestions keep annoying me when i want to indent
                    ['<S-Tab>'] = cmp.mapping(function(fallback)
                        if cmp.visible() then
                            cmp.select_next_item()
                        elseif luasnip.expand_or_jumpable() then
                            luasnip.expand_or_jump()
                        else
                            fallback()
                        end
                    end, { 'i', 's' }),
                },
                sources = {
                    { name = 'nvim_lsp' },
                    { name = 'luasnip' },
                },
            }

            vim.diagnostic.config({
                underline = false,
                signs = true,
                virtual_text = true,
                float = {
                    show_header = true,
                    source = 'always',
                    border = 'rounded',
                    focusable = false,
                },
            })
        end,
    },
}

Calling require('which-key').register({}, {}) after last keybindings makes it recognize F3 but not F2 for some reason..