use stduse sysuse thread const main = {	var f 	f = thread.mkfut()	thread.futput(f, 123)	std.assert(thread.futget(f) == 123, "the future is broken\n") 	f = thread.mkfut()	thread.spawn({		std.usleep(10_000)		thread.futput(f, 321)	})	std.assert(thread.futget(f) == 321, "the future is broken\n")}