Why wont this chat message system work?

Not sure what the problem with this script is but its not working

local function chat(message)
    game.StarterGui:SetCore("ChatMakeSystemMessage", {Text = message, Colour = Colour3.FromRgb(255, 255, 255), Font = Enum.Font.SourceSansBold})
end

local messages = {"Test"}

while true do
    wait(5)
    chat(messages[math.random(1, #messages)])
end