He also mentions the elastic beanstalk support for Docker from April. It's quite obvious that everyone has been working on Docker support for a while now anyway.
The go community reminds me of the java community. Blind faith in the design decisions of the language. Any feature it doesn't have is passionately defended as a good decision because the clumsy old way is subjectively clearer, up until the day it gets added.
Go is pretty low level compared to (even) java, not much of a win in terms of expressiveness or error handling. Seems like a lot of effort with minimal benefit.
Groovy performance is pretty poor in general and is mostly used for writing build scripts. It's a scripting language whereas Scala and Kotlin are better suited to writing large systems. Groovy seems to have stagnated outside of its use with gradle, whereas Scala continues to grow.
Kotlin is very similar to Scala, but far less ambitious and not as focused on functional programming. In fact there have been various posts pointing out the similarities between Scala and Swift. It's rather pragmatic but there hasn't been much interest in it so far. Perhaps things will pick up after hitting v1.0. Pitching it as a Java substitute for Android would be a clever move. Java 8 is a poor substitute for Kotlin or Scala, and on Android you're stuck on even more archaic syntax. I'd be glad to see Kotlin replace java on Android.