Git-go is a variation of the word get-go, which means at the start or beginning. It is usually found in the phrase from the get-go. As a compound noun it is always hyphenated.
Get-go is used vastly more often than git-go. The word was first used in the United States in the sixties by an African American writer. There is no conclusive evidence for where the term derived from. One guess is the phrase from the word go and another is a shortened version of get going.
Git on its own can be a mean or unruly person, or a variant of get. This spelling variation also appears in the phrase git-r-done, which is found mainly in the United States to mean finish your work no matter what.
Examples
Richards may have had his doubts about Iraq in March 2003, but he tells me that he firmly supported the invasion of Afghanistan from the get-go in October 2001. [Huffington Post UK]
“He brought us size, tenacity and a booming shot, and was an intimidating presence on our team right from the git-go.” [Sun Sentinel]
Neither Sairam Shankar nor Adonika seem to understand the nuances of romance and right from the word go they resort to over the top histrionics. [Times of India]
Whatever transpires, you can rely on some trolls or genuinely stupid people using it to throw death threats or be a git to someone. [Bitter Wallet]
They laid them out as ambushes for the English, and just to prove how stupid and unobservant they were, the Scots stuck flags in them, but the gits fell for it anyway, then built clubhouses that wouldn’t let women in except on alternate Wednesdays and for dinner dances, and then only if they were accompanied by a male member. [GQ]
I flapped my arms and shouted “Git! Git! Go on!” [Pocono Record]
I remember the old westerns in which the bad guy has escaped and the sheriff bellows out, “I’m deputizing every last one of you men—we’ll git that varmit.” [Met News]