Student or Learner
I discovered that I have some difficulties pronouncing ŋ in 'ing'-endings (going, making, singing etc) when the next word starts with a vowel (for instance, learning English). I always tend to change it to 'n' if I try to pronounce this type of phrases quickly.
How's it in ordinary speech? Though it's pronounced quickly it doesn't seem to change to 'n', does it?
P.S. What's the difference in pronunciation, say, going when it's indicated as goin'?
I think in ordinary speech, most people wouldn't produce the 'ng' sound exactly as a velar nasal /ŋ/, but would do as you do; make it a /n/ sound.
That is what the omission of 'g' signifies in words like goin'. Unless the /ŋ/ was followed by a back sound, it is most likely produced as /n/.
The only time it would cause any confusion is if the /ŋ/ sound was a minimal pair. Compare:
I wing all the competitions.
I win all the competitions.
'Wing' here is used in this sense: "to accomplish or execute something without sufficient preparation or experience; improvise".
In such a case the velar nasal is required. In general though, confusion or misunderstanding would be minimal if /n/ replaced /ŋ/.