PHP, with Composer and Laravel is really great. There is a fully featured VM compatible with Laravel out of the box called Homestead, and it mirrors some of the more standard test/stage/prod environments out there.
git clone https://github.com/laravel/homestead.git ~/Homestead
Or, if you’re on Windows:
git clone https://github.com/laravel/homestead.git /c/Users/userName/Homestead
That sets up the VM “globally”, and you can edit the Yaml file to work with directories, databases, etc. Use Vagrant to work with the VM. If you’re on Windows you can ssh in PowerShell using vagrant ssh or the PowerShell ssh is in Beta, and it’s been really, really, really nice.
Composer is really easy, especially if you’ve ever used Homebrew, Chocolatey, Pip, or anything like that.
composer require global "laravel/installer=~1.1"
and BOOM, you’re done.
Well, you’re not done, but you get the idea
PHP is still the dominant language out there, especially when freelancing (in my experience).
There is a great podcast and book to assist you with Laravel. The book is Mac focused, but the code works on Linux and Windows.
The Podcast and book are by the same person. I am not affiliated in any way with the author, but his book did help me tremendously, in a non-Mac environment (Windows).
Now, regarding your second question… I agree that Go is pretty popular, and it’s quickly overtaking Python in the infosec realm. There is also an insane amount of work you can do with just the standard library. It’s literally mind boggling.
Clojure is awesome, as well. You can do web dev, among other things as well. It’s a fascinating language, and based off of Lisp from what (little) I understand.
If you’re a fan of Ruby, you might try Scala? Scala, as well as Clojure, are JVM languages, but they’re very flexible and a lot of fun.