https://underscore.io/books/essential-scala/
https://underscore.io/books/scala-with-cats/
https://www.manning.com/books/functional-programming-in-scala
https://academy.lightbend.com/
https://www.udemy.com/course/rock-the-jvm-scala-for-beginners/
https://www.udemy.com/course/advanced-scala/
https://www.scala-exercises.org/