By default, the app will follow the theme of your phone in general. If you’re on Android 10 or iOS 13, and is using dark mode, then the app will show up in the mode automatically. You’ll also get the ability to switch between light and dark modes in the app’s settings. Those running older operating systems will have to access dark mode for the Google app this way.
— Google SearchLiaison (@searchliaison) May 19, 2020 The dark mode rollout has been staggered between the multiple Google apps on mobile, which is weird in its own way. So far, Gmail, Calendar and Keep are some of the apps that have gotten dark mode. With this new addition, this leaves Maps as another prominent Google app that hasn’t yet gotten the mode. At any rate, if you frequently use the Google app and have not yet gotten the update, you should check to see if the update has been made available to you yet. If not, maybe give it another go at the end of the week. (Source: Google / Twitter)