There are a lot of misconceptions about working out while on a ketogenic diet.
When starting to work out on keto, the first thing you need to determine is your goal. If your goal is weight loss you need to be at a calorie deficit. While you're generally eating higher quality foods on keto, you can totally undo an hour on the treadmill by going home and eating a block of cheese (even though you may still be in ketosis). Not all calories are created equal—100 calories from a cookie are completely different than 100 calories from veggies. Focus on foods that are nutrient-dense and satiating.
If your goal is to gain muscle, you need to make sure you're eating enough protein. Some people claim that eating too much protein will kick them out of ketosis through gluconeogenesis, although this doesn't consistently happen to everyone. If you want to build more muscle a higher protein macro is generally needed.
For either of these goals, you need to use fat as a lever in your meals and also make sure you're getting enough electrolytes to prevent fatigue. If you're still feeling tired during your workouts, consider trying cyclical keto and cycling in high-quality carbs.