ㄍ一ㄥ? What dialect? What character?
This wikipage says that 台語正字 is 矜/楗(教育部用字). 

Also this online dictionary of Taiwanese dialect lists 楗 to be the character in question.

However, it is possible that neither is the true character. They just made up some characters in order to transcribe the word. The ancient phonetic books describe that 楗 rhymes with 偃/鍵/建/件, which rhyme with -ian or -iann in Taiwanese， not -ing. On the other hand, 矜 has a historic pronunciation that ends with -m instead of -n or -ng, and the meaning does not really match 硬撑 either. A wild guess of mine is that the character might be 经/擎.