Swep open menu need help

hello i have a problem with swep (sorry for my english i’m french ) error : shared.lua:57: attempt to index global ‘umsg’ (a nil value)
my shared.lua code


function SWEP:PrimaryAttack()
	local tr = ply:GetEyeTrace()
	if tr.Entity:IsPlayer() then
				
		umsg.Start("RP_FineMenu", ply)
			umsg.String(tr.Entity:Nick())
		umsg.End()
				
	end
end

use netmessages, not usermessages.