In terms of technologies, JavaScript is here to stay for many years and depending on the industry can be very profitable, too. A LAMP background lends itself to

In terms of technologies, JavaScript is here to stay for many years and depending on the industry can be very profitable, too. A LAMP background lends itself to branching out to other web-based technologies. JavaScript will be a natural extension to your current skill set. However, I'd advise against focussing on a technological niche alone. I'd suggest focussing on a business niche (industry, specific business problem) and additional skills that are complementary to coding (teaching, consulting). Try to position yourself as a business problem solver rather than someone who turns requirements into computer code. Learning something completely new such as Golang or mobile development only makes sense business-wise if you already have customers who might be interested in that. There's nothing wrong with learning new skills but in terms of business success learning a new technology - especially if it's a relatively new one such as Golang - is equivalent to developing a polished product before having the first customer or in other words: The exact opposite of the Lean Startup / MVP way of doing business.