Python and Ruby are both dynamic while Go and Kotlin are statically typed. For me statically typed always wins against not-static but in your case coming from Javascript you'll be more familiar without types.
Ruby is a really easy language to grasp and use. If you are looking for development speed then Rails is your goto. The bad side is that ruby has no support for async operations.
Kotlin has all the support of the Java ecosystem behind it. You can use all their libraries and already have great frameworks for backend stuff.
Go is the new kid on the block. It's cool to use if you are looking for something fast but it's the most basic of the 4 languages in terms of syntax and you have to get used to pointers.
If you are looking for speed go with Rails or python with Django. If you are looking to learn you could take a look at Kotlin and use types along the way.
All of those languages have their pros and cons:
If you are looking for speed go with Rails or python with Django. If you are looking to learn you could take a look at Kotlin and use types along the way.
Thanks for your insights! It is really hard to decide.