When a suffix is added to a word ending “-ng”, the ŋ* is usually retained (“singing”) except for a few suffixes such as comparative “-er” and “-est” (“longer”, “strongest”, which have ŋg**).

In the list below, words ending in “nger” are pronounced:
* Without a hard “g” sound.
** With a hard “g” sound.
*** With a “jer” sound.

This is a partial list of words ending in “nger”:

anger **
challenger ***
hanger *
danger ***
stranger ***
exchanger ***
finger **

 https://www.quora.com/How-do-I-pronounce-singer-and-stronger