I'm uncertain about the grammar of this sentence. Which of the following two would I write?
He goes on to say that…
He goes on to saying that…
I googled both of these phrases. The former seems to be more common (though many instances of the latter are seen). In Google's ngram viewer, however, it seems that the latter doesn't even exist.
Best Answer
Collins lists the first construction here as [verb + particle (on) + to-infinitive]:
It also lists a construction similar to the second, but as [verb + particle (on) + preposition (to) + noun (place)]:
A metaphorical broadening of this, and the use of an ing-form in place of the noun, are not unacceptable per se:
That's all for today. We go on to knitting cardigans next week.
But 'He goes on to saying that ...' is a poor, probably unacceptable, replacement for 'He goes on to say that ...'. This broadened sense (We go on to knitting cardigans next week.) can be paraphrased by, for example, We go on to look at / cover knitting cardigans next week. or We move on to knitting cardigans next week.