[yason]

That's how I learned English. Not in school but because I was programming and my native language was lagging a couple of decades behind when it came to programming materials and books.

And once you use it for programming, it's logical to use it for asking questions on the Usenet (then) or internet forums (today), and reading papers on interesting subjects, and communicate with your peer programmers or contacts around the world. By then you realize how much you would lose in any translation which makes you want to read any novels written in English too and watch films without subtitles. And eventually you land your first job where you also need to speak English in addition to your native language, and maybe in your second job English is the primary language of the company and you only use your native one for chitchatting locally over a cup of coffee. Roughly, by that time, English has slowly become the second native language in your life.