If your watch battery is not lasting a whole round, there are a few things you can do to optimize battery usage. The key is to turn off sensors that you do not need, which tend to consume the most battery.
First of all, turn off the heart rate sensor. A golf game is considered a workout, and Apple Watch turns on the heart rate sensor by default. If you do not care about measuring heart rate while playing golf, go to the Apple Watch app on your phone, in the first tab, find Privacy->Motion & Fitness->Heart Rate, and turn it off. See screenshots below. This can typically save 50% of your battery, so we highly recommend it.
Beyond that, you could turn off motion sensors, which we use to track your golf swings. There are several ways to turn them off, in increasing power consuming order:
You cannot turn off the GPS sensor, which we need to measure your location, giving your real-time distance to the hole.
At the end of your game, you must terminate the session for the motion sensors to stop consuming battery. If you see the green workout icon on top of your watch, the workout session is still on, and the motion sensors (if used) and GPS are still consuming your battery.