Engineering Ethics is a standard required class in any engineering discipline and a whole field of discussion. The ethics of working on military stuff (or even just government stuff) is nowhere near as cut and dry as your question seems to imply.

For example:

- What if the country asked you to develop technology to track and hack journalists or political rivals the administration doesn't like?

- What if the country asked you to develop chemical weapons? Is it different if the weapons would be used on their own population or only on external "enemies"?

- What if the country asked you to personally assassinate a civilian of another country? What if they asked you to create a program that would do that? What if they asked you to simply create a list of targets, and you knew they'd be assassinated?

- What if the country asked you to build something in an unsafe way that you're pretty certain will cause harm to people?

- What if the country asked you to make a public statement lying about the purpose behind what you're building?