I'm probably the exact opposite, I'm more a Jack of all trades, master of none. I jump from language or framework to another without any remorse, just trying to do the best given time, resources and project needs. I did work with c (text template engine lib / x11 gui app / personal kernel module / dpdk userspace networking / arduino & pi baremetal stuff / ...), C++ (mostly some qt stuff for my old blackberry Q10), Java (I'm probably one of the few who liked Swing...), Go (backend servers), Python 2/3 (Some webdev, mostly admin scripts), PHP 4-7 (web/cli...), js (basic stuff and jQuery, trying to get into dart and flutter next...)

When I try to see my self in the shoes of a primary C dev, I wouldn't see Go as a concurrent to C, but more as a less annoying scripting language. Every time when I switch from a "typed" to an "untyped" language, I do need a longer time to "feel at home" again. Therefore I think Go could be good language for a C dev for small tasks on the site, like creating small cli tools for the buildchain or generally inhouse, things like that what one normally tends to look at python for. Go makes it easy to create a good cli interface, easy to document the format of a config file and writing a test. Deployment is also easy thanks to that is just a static blob that comes with everything that it needs. So no worrying about if the right interpreter is installed on that dev server, just copy it over with scp and it works.