Why won't this KeyDown Function that's supposed to add speed work?

I made this small script and placed it in StarterPack but it's not working. It's supposed to add 50 speed everytime I press "q".

player = game.Players.LocalPlayer
mouse = player:GetMouse()
c = player.Character
h = c.Humanoid
ws = h.WalkSpeed

mouse.KeyDown:Connect(function(key)
	if (key == "q") then
		ws = ws + 50
	end
end)

I have not tested it out, it might not work. An important thing is that you should put local before each of your variables. An another important thing that you should use is UserInputService or ContextActionService, both of those services do a lot(ContextActionService can create custom buttons on the screen and with UserInputService, you could check what device the player is using and much more stuff)

local player = game.Players.LocalPlayer
local uis = game:GetService("UserInputService")
local char = player.Character
local hum = char.Humanoid
local amount = 50
uis.InputBegan:Connect(function(key, gpe) 
	if key.KeyCode == Enum.KeyCode.Q and not gpe then -- gpe stands for GameProcessedEvent
		hum.WalkSpeed = hum.WalkSpeed + amount
	end
end)