Dexophobia

In my program, when it ends it crashes the entire computer, what might be happening here?

io = require("io")

io.write("Press w")

while true do

    input = io.read()

    if input == "w" then

        break

    else

        io.write("Wrong key!")

    end

    io.write("Correct key!")

The Error is:

/bin/sh.lua:14: attempt to index field 'stdin' (a nill value)

stack traceback:

init:18: in function <init:17>

(...tail calls...)

/bin/sh.lua:14: in main chunk

[C]: in function 'xpcall'

machine:798: in function 'xpcall'

init:17: in function 'init'

bios:64: in main chunk

it started after i added io.read()