perlnavigator root_dir setting

[ashrasmun]

Hello,

I would like to setup config for perlnavigator. So far I've been doing it this way:

local nvim_lspconfig = require('lspconfig')

nvim_lspconfig.perlnavigator.setup {
    single_file_support = false,
    root_dir = nvim_lspconfig.util.root_pattern('README.md')
}

However I understand I should have it set up in mason's setup_handlers function. Using https://github.com/nvim-lua/kickstart.nvim as reference, I understand I should have the aforementioned setup section placed in servers array, just like I have it set up with lua_ls:

local servers = {
    lua_ls = {
        Lua = {
            workspace = { checkThirdParty = false },
            telemetry = { enable = false },
            diagnostics = {
                disable = { "missing-fields" },
            }
        },
    },
    -- perlnavigator = {???}
}

I've tried setting up the root_pattern in perlnavigator section, like that:

local nvim_lspconfig = require('lspconfig')
local servers = {
    lua_ls = {
        Lua = {
            workspace = { checkThirdParty = false },
            telemetry = { enable = false },
            diagnostics = {
                disable = { "missing-fields" },
            }
        },
    },
    perlnavigator = {
        single_file_support = false,
        root_dir = nvim_lspconfig.util.root_pattern('README.md')
    },
}

however I get an error:

C:\Users\...\AppData\Local\nvim-data/lazy/lazy.nvim
Error executing vim.schedule lua callback: D:/tools/neovim/share/nvim/runtime/lua/vim/lsp/rpc.lua:288: Cannot serialise function: type not supported
stack traceback:
	[C]: in function 'encode'
	D:/tools/neovim/share/nvim/runtime/lua/vim/lsp/rpc.lua:288: in function 'notify'
	D:/tools/neovim/share/nvim/runtime/lua/vim/lsp.lua:1335: in function 'cb'
	vim/_editor.lua:263: in function <vim/_editor.lua:262>

What am I missing here?