/n/ → /ŋ/
Here the /n/ is followed by a sound that is produced at the back of the mouth, a velar (a /k/or a /g/), so the nasal alveolar /n/ is turned into a nasal velar /ŋ/. As you can see, the place of articulation changes, but the manner is the same.
Therefore,
/n/ (followed by /k/ or /g/) becomes /ŋ/
One king. ǀ wʌŋ ˈkɪŋ ǀ
Then go for it! ǀ ˈðeŋ ˈgəʊ fər ɪt ǀ