Simple DataStore script keeps returning an error?

My DataStore script isn't working it keep getting an error saying that GetAsync() is not a valid member of datastore?

local datastore = game:GetService("DataStoreService")
game.Players.PlayerAdded:connect(function(player)
	local leaderstats = Instance.new("IntValue")
	leaderstats.Name = "Stat"
	leaderstats.Parent = player
	local stata = Instance.new("BoolValue")
	stata.Name = "NewPlayer"
	stata.Parent = leaderstats
	local key = "user-" .. player.userId
	local storeditems = datastore:GetAsync(key)
	if storeditems then
		stata.Value = storeditems[1]
	else
		local items = {stata.Value}
		datastore:SetAsync(key, items)
	end
end)
game.Players.PlayerRemoving:connect(function(player)
	local items = {player.Leaderstats.Stat.Value}
	local key = "user-" .. player.userId
	datastore:SetAsync(key, items)
end)