How do I include kotlinx.coroutines.experimental ? In my project, which I'm starting from new

why don’t you use stable coroutines?

Actually I have an old piece of code that I want to reuse, and it uses Ktor 0.9.5 and Ktx 0.30.1

Why not update to stable coroutines?

Idk, I did have to work on the Ktor part of the code too.

ktor has been updated to stable coroutines since then

I agree with other people in this thread, I wouldn't spend any time on support of experimental coroutines in your project, instead migrate on stable ones

No worries, set the gradle project wrongly.