etc/nvim/lua/indent.lua

-- Golang, C based configuration
vim.o.autoindent = true
vim.o.foldmethod = 'indent'

createAutoCmd = vim.api.nvim_create_autocmd

-- Basic thing for compiling languages.
createAutoCmd({
  "BufNewFile",
  "BufRead",
},{
  pattern = "*.go,*.c,*.cc,*.C,*.cpp,*.rs,*.mk",
  callback = function()
    local buf = vim.bo[vim.api.nvim_get_current_buf()]
    vim.o.expandtab = false
    vim.o.tabstop = 4
    vim.o.shiftwidth = 4
  end,
})

createAutoCmd({
  "BufNewFile",
  "BufRead",
},{
  pattern = "*.txt,*.lua,*.js,*.jsx,*.scss,*.css,*.sass,*.html,*.htmlx,*.tmpl,*.tpl,*.yml,*.yaml,*.toml,*.tml",
  callback = function()
    local buf = vim.bo[vim.api.nvim_get_current_buf()]
    buf.expandtab = true
    buf.shiftwidth=2
    buf.tabstop=2
    buf.softtabstop = 0
  end,
})

createAutoCmd({
  "BufNewFile",
  "BufRead",
},{
  pattern = "*.md,*.py",
  callback = function()
    local buf = vim.bo[vim.api.nvim_get_current_buf()]
    buf.expandtab = true
    buf.shiftwidth=4
    buf.tabstop=4
    buf.softtabstop = 0
  end,
})