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In Old English, [ŋ] was always followed by either [k] or [g]. Modern English words that end in [ŋ] without [g], like sing, show the result of a change of word-final [ŋg] to [ŋ] (this change did not occur to completion in all dialects).
Word-internal [ŋg] mostly remained (as in finger, anger), but...