Shift to sprint script is not working. Maybe I accidentally pressed the wrong key? [closed]

This is the Shift To Sprint Importer script:

function onPlayerEntered(player)
   repeat wait () until player.Character ~= nil
   local s = script.SprintScript:clone()
   s.Parent = player.Character
   s.Disabled = false
   player.CharacterAdded:connect(function (char)
      local s = script.SprintScript:clone()
      s.Parent = char
      s.Disabled = false
   end)
end

game.Players.PlayerAdded:connect(onPlayerEntered)

This is the Shift to sprint local script:

local mouse = game.Players.LocalPlayer:GetMouse()
local running = false

function getTool()
for _, kid in ipairs(script.Parent:GetChildren()) do 
    if kid.className == "Tool" then return kid end 
end
return nil
end


mouse.KeyDown:connect(function (key) --Run function
      key = string.lower(key)
      if string.byte(key) == 48 then
           running = true
           local keyConnection = mouse.KeyUp:connect(function (key)
                if string.byte(key) == 48 then running = false 
          end
      end)
      game.Workspace.CurrentCamera.FieldOfView = (70+(1*2))
      wait()
  end
  game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 16 
  for i = 1,5 do 
      game.Workspace.CurrentCamera.FieldOfView = (80-(1*2))
      wait()
  end
end)

Help would be greatly appreciated..