It wouldn't be a major phone launch without some teething troubles, and the iPhone XS appears to be no exception to the rule. Some device owners on Apple's forums, Reddit and Unbox Therapy (among others) have reported that their units won't charge properly through the Lightning cable until the screen wakes up. In certain cases, it won't work until you both wake the screen and reconnect. Suffice it to say this could be inconvenient if you plugged in at night and were counting on a full charge the following day.
Wireless charging appears to be normal.
We've asked Apple for comment on the issue. It's not certain if the problem is hardware- or software-related, although the company has fixed charging issues through software in the past. It just recently patched an Apple Watch bug that prevented devices from charging, for instance. We wouldn't be surprised if there's an update on the way in the near future -- while this isn't a crippling issue, it's more than a little irksome if you invested a ton of cash in Apple's latest smartphones.