Does anybody know how to make a simple shift to sprint script?

I know there used to be a really simple way. I want it to be easy to modify and when pressing shift you sprint. I used to know how but the code has changed and i dont want to use free models

It's still pretty simple to do. All you have to do is this:

local UIS = game:GetService("UserInputService")
local plr = game.Players.LocalPlayer

UIS.InputBegan:Connect(function(obj, gp)
	if obj.KeyCode = Enum.KeyCode.LeftShift and not gp then

plr.Character.Humanoid.WalkSpeed = 0 --change this to what you wish the speed to be

end
end)

I can also allow you to change it back to normal when you hit it again. If you wish to have it be held, then this script would not work however.