"Press any key" example in Lua with POSIX module.

anykey.lua

local bit = require "bit"
local termio = require "posix.termio"
local unistd = require "posix.unistd"
local inspect = require "inspect"

local t = termio.tcgetattr(unistd.STDIN_FILENO)
local o_vmin, o_vtime, o_lflag = t.cc[termio.VMIN], t.cc[termio.VTIME], t.lflag

io.stdout:write("Press any key... ")

-- blocking read for 1 byte
t.cc[termio.VMIN] = 1
t.cc[termio.VTIME] = 0
t.lflag = bit.band(t.lflag, bit.bnot(bit.bor(termio.ECHO, termio.ICANON)))
termio.tcsetattr(unistd.STDIN_FILENO, termio.TCSANOW, t)

local ch = io.read(1)

-- in case of escape sequence, do polling read to get the rest of bytes
if ch == "\27" then
   t.cc[termio.VMIN] = 0
   termio.tcsetattr(unistd.STDIN_FILENO, termio.TCSANOW, t)
   repeat
      local b = io.read(1)
      if b then
         ch = ch .. b
      end
   until not b
end

t.cc[termio.VMIN] = o_vmin
t.cc[termio.VTIME] = o_vtime
t.lflag = o_lflag
termio.tcsetattr(unistd.STDIN_FILENO, termio.TCSANOW, t)

print("\nYou pressed: " .. inspect(ch))