You can learn Kotlin by reading its documentation and getting started quickly, or take your time and read a book. I prefer books. I like the story aspect of books.
Of all the books I have read, I especially like “Kotlin in Action”.
It’s written by the authors of Kotlin, so they probably know what they are talking about. They also explain the “why” behind some of Kotlin’s features, making reading more interesting.
The first edition doesn’t have chapters on Co-routines since it didn’t exist when the book was written. The latest edition has chapters on co-routines. I have yet to read the Second Edition.