Heat the oil in a large pot over medium heat. Add the sausage and stir-fry for 3 minutes, breaking it up as it cooks. Add the onion and celery and stir-fry for 5 more minutes. Add the chicken stock, bring to a boil, decrease the heat, and simmer for 10 minutes. Add the bamboo shoots, mushrooms, and coconut milk. Simmer for 2 more minutes. Add the lime juice and taste for salt and pepper. Serve garnished with green onions and cilantro leaves.