Limit Notation: $ \lim_{x \to \infty} f(x) =\infty $ or $ \lim_{x \to \infty} f(x) \rightarrow \infty$?
You have two usual notations :
$$(1)\qquad \lim_{x\to+\infty}f(x)=+\infty$$
and
$$(2)\qquad f(x)\xrightarrow[x\to+\infty]{}+\infty.$$
So in your case, the first one is correct.
(The second one is not appropriate because $\to$ usually means tends to, and a limit is equal to something.)
First one is correct; "→" generally means "tend(s) to". Limits either equal something (or +/- inf) or don't exist; they do not tend to something.
The first one is correct, the second one is incorrect.