Heat olive oil in a skillet over medium heat. Cook and stir onion and garlic in hot oil until fragrant, about 2 minutes.
Season goose with salt and pepper; add to the hot oil. Cook goose breast slices in hot oil for 2 minutes, flip, and continue cooking until evenly browned, about 2 minutes more.
Pour chili sauce over the goose; reduce heat to medium-low and cook at a simmer until the chili sauce thickens, about 3 minutes.