Goto's work on a local scope, ie. they'll only jump to a point defined within the same event/alias. The command parameter of a call to /timer is executed in a different scope to the calling alias, if it weren't then the alias wouldn't be able to return or end until the timer had expired (after 15 seconds in your case).
I can't really give a fix for the problem since if your code worked as you expected it would create an infinite loop, which of course is not what you want.
P.S. Both the interval and repetitions parameters are necessary for the timer command to work.
