[Wasabista]

Sorry if I "daburu" what others have said.

According to a Japanese linguist named Mizutani, there have been educational fashions on this topic. It used to be that the intervocallic (between vowels) pronunciation "ng" (as in "singer" not "finger") was favored; later, the "g" sound came into educational favor. However, both are correct.

You will notice that the "ng" sound is popular with older people and with enka songs. I personally prefer the intervocallic "ng" pronunciation.