Hammerspoon (https://www.hammerspoon.org) script to add a custom key binding for vim mode in Xcode. Pressing two times the f-key within the time frame exits insert mode in normal vim mode.

init.lua

local timer = require("hs.timer")
local eventtap = require("hs.eventtap") 
local keycodes = require("hs.keycodes")
local events = eventtap.event.types
local timeFrame = 0.2 
local f_key = 3 
local pressTime, firstDown = 0, false

function twoHandler()
    local frontmostAppName = hs.application.frontmostApplication():name()
    if frontmostAppName == "Xcode" then
        hs.eventtap.keyStroke({"ctrl"}, "h", 100, frontmostAppName)
        hs.eventtap.keyStroke({"ctrl"}, "h", 100, frontmostAppName)
        hs.eventtap.keyStroke({""}, "ESCAPE", 100, frontmostAppName)
    end
end

function isKeyCorrect(event) 
    local keyCode = event:getKeyCode()
    return keyCode == f_key 
end

function inTime(time) 
    return timer.secondsSinceEpoch() - time < timeFrame
end

keydown = eventtap.new({ events.keyDown }, function(event) --keep keydown globally to ensure it stays alive
    if isKeyCorrect(event) then 
    if firstDown and inTime(pressTime) then --if first press already happened and the second was in time
        twoHandler() 
    elseif not firstDown or not inTime(pressTime) then --if the first press has not happened or the second wasn't in time
        pressTime, firstDown = timer.secondsSinceEpoch(), true --set first press time to now and first press to true
        return false --stop prematurely
    end
end
pressTime, firstDown = 0, false --if it reaches here that means the key was incorrect, then reset timer and flag
return false --keeps the event propagating
end
) --start our watcher
keydown:start()