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Twelfth Night,
Act 3, Scene 4, line 95.

Note to Twelfth Night, 3.4.95, "Go to, go to"

"Go to" is an all-purpose phrase, meaning (according to the Oxford English Dictionary) "to go about one's work, to get to work," and used to "express disapprobation, remonstrance, protest, or derisive incredulity." So it's used the way we use various phrases such as "mind your own business," "omigod," "you don't say," "you've got to be kidding," etc., although for Sir Toby, "go to" seems to be just a noise he makes while he thinks of what to do next.

Simon Armstrong as Sir Toby Belch
Sir Toby Belch