【go bad】 —

1. (of perishable products) become unfit for consumption or use:

• Fish and meat soon 【go bad】 in hot weather.

2. be unsuccessful:

• It sometimes happened, Gertrude admitted, that an artist’s work went bad and she lost interest in him.

3. stop functioning:

• They know how to record and the tapes are good, but not long ago their machine went bad and they didn’t know it.

Note: The expression does not correlate in meaning with the phrase go to the bad—

1. become completely immoral:

• Vince sobbed that it was too late and he had already “gone to the bad.”

2. have financial difficulties:

• The collapse of Enron acts as a reminder that socially bad companies often go to the bad financially, too.

【go badly】 — = 【go bad】 2:

• It felt like the work went badly this time, but other people seemed impressed with how much we achieved.