C172 pilot reported that while making an approach to the airport where they executed a go around; the aircraft was climbing slow resulting in the pilot turning to avoid terrain. After reaching a safe altitude; the pilot departed the airspace.

Narrative

I was coming in to landing at ZZZ on a cross country. Was planning a low approach; but airspeed was looking good enough to practice a slip to landing. I rounded out on runway XX at around 75kts; airspeed went up a bit during the slip. I was on centerline and everything was going good; but decided to go missed due to ZZZ having a shorter runway. I was at around 55kts when I put full power in. Our original plan was to depart to the south east. After applying full power; the aircraft was climbing slower than I liked to see for the situation; and I could see some lights on the hill in front of me; so I decided to turn S/E for the departure to avoid the rising terrain. After making the turn; I still didn't like my climb rate; and though I would easily clear the terrain in front of me; I decided to continue in the turn because ZZZ Traffic pattern is over flat terrain. I was around 200-300 AGL when I made the turn to parallel the runway. When I climbed to a safe altitude; I turned back to S/E and departed the airspace. There were not any other aircraft in the pattern; no injuries; no damage to property. Maybe some upset home owners; but this was a PIC decision I made to ensure everyone's safety. I definitely learned a valuable lesson on this approach.