This is another (non-anonymous) vote for Go (golang). Here are some reasons:
* Type Safety
For any serious project type safety provides a massive boost to productivity and correctness. Go's type system is powerful but not too intrusive to more generic coding.
* Fast compilation
Although it is not interpreted the language and package design allow very fast compilation so that it can be treated as a scripting language and compiled at run time.
* Good libraries
There is a large and growing collecting of libraries, mainly focussed on web service applications but other areas are also supported. You can create a web server that handles multiple concurrent requests in a single page of code.
* Good package (module) support
Go provides the ability to create packages with a certain amount of encapsulation and data hiding without it being a burden on development time.
* Built-in concurrency
Language support for concurrent execution and synchronised communication makes it very easy to develop modular applications that support multiple activities.
* Clean Syntax
Go code is easy to read and missing lots of fluff from other languages. The gofmt command tidies up code and makes it consistent throughout a project
* Built-in unit test framework
Go makes it easy to check that you code does what it is supposed to
* Good performance
Not quite up to C++ standards but faster than interpreted solutions
* Can generate JavaScript!
There are at least two solutions for converting Go code to JavaScript, so you can can use one language for client and server code.
I also like the type system (interfaces) and other language features, but these are more a matter of taste.