Sefer Chofetz Chaim hilchos Rechilus chapter 1 halachos 6, 7

There is a halacha in Shulchan Aruch Yoreh Deah 157:1 in the Rema that one must be ready to lose all his money to not transgress a prohibition. The Pischei Teshuva (4) says that even applies to rabbinic prohibition, then all the more so for severe Torah level prohibitions like rechilus. You can’t speak rechilus even if you might lose all your livelihood, for example if your boss is trying to convince you to rattle on someone and there is nothing positive that can come out of it then you must be ready to lose your job then to speak rechilus. It is obvious that losing your livelihood is not kin to dying so you mustn’t transgress the sin even though if it’s a question of dying or sinning one is allowed to transgress any sin besides adultery (incense), idolatry, and murder. Definitely if all that will happen is that he will curse you out and speak badly about you even in public if you don’t answer his questions and tell on the person, he is inquiring about you still have to be ready to take anything he says with silence and not transgress rechilus. If you stay quiet in this world then you will be one of the beloved of Hashem in the Next World with a shining face like the sun as it days in Yoma 23a “Those insulted and they don’t insult back, they hear people cursing them and don’t answer… about them the verse in Shoftim (5:31) says “And his loved one like the setting of the sun at its peak.” Now of course if answering his questions will lead to something constructive then you can answer his questions assuming use abide by the parameters that will be discussed in chapter 9.