Green’s Dictionary of Slang

(Aus.) a goanna.

1900		Bulletin (Sydney) 7 July 14/2: I found a large black-and-yellow gent with all that remained (about a foot of tail) of a brother ‘go.’ sticking out of his mouth.
1901		Bulletin (Sydney) 13 July 15/1: When James rushed, the go. slid up a tree with the strings of the leather bag hanging from its mouth.
1912		Dubbo Dispatch (NSW) 29 Mar. 7/8: When last seen the old chap had an enormous black and white ‘go’ tied up with a chain.
1955		N. Pulliam I Travelled a Lonely Land (1957) 186: Since the real iguana doesn’t live in Australia, ‘goanna’ — sometimes shortened to ‘go’ — has become firmly accepted.
1969		L. Hadow Full Cycle 139: If there’s any blue this time, I’m heading north like a go up a tree. They can stick this joint.