How do I make this function stop after 20 seconds?

I tried making it so that when a person touches this part it rains bombs from the sky for 20 seconds and stops after. Since nothing was working, I even tried making a separate brick to stop the function, but I do not know if that works at all..

how will I make the raining stop after 20 seconds?? :(

here is my code

local bomb = game.ReplicatedStorage.Bomb:clone()
game.ReplicatedStorage.Bomb.Anchored = false
local player = game.Players.LocalPlayer
local bridge = game.Workspace.Bridge
local bombactivator = game.Workspace.BOMBING

local function skybombing()
	while true do
	local bombClone = bomb:clone()
	bombClone.Position = Vector3.new(math.random(-500,500),500,math.random(-500,500))
	bombClone.Parent = game.Workspace
	bombClone.Anchored = false
	wait(1)
	if wait(20) then break
		
	end
	end
end

bombactivator.Touched:Connect(function(Touched)
	if Touched.Parent:FindFirstChild("Humanoid") then
		wait(1)
		bombactivator.BrickColor = BrickColor.Red()
		skybombing()
	end
end)

Hi.

Instead of using while loop use for loop:

for i = 1, 20 do
	local bombClone = bomb:clone()
	bombClone.Position = Vector3.new(math.random(-500,500),500,math.random(-500,500))
	bombClone.Parent = game.Workspace
	bombClone.Anchored = false
	wait(1)
end