iPhone users REJOICE! In an announcement today, Niantic Labs announced that they are working on the fix to make Ingress compatible with iOS 12.
If you have an iPhone or iPad, you should still hold off on upgrading to iOS 12 until the fix is complete and tested if you plan on playing Ingress though.
We are happy to report that the current version of Ingress will soon be compatible with iOS 12. Since its release earlier today, we have been working to resolve incompatibilities. We are optimistic that we will be able to release an update to Ingress for download via the App Store in the coming days