It comes down to how the standard library makes you do things. I don't think there's any reason why a more stringly-typed way of handling JSON (or, indeed, a more high-level way of using HTTP) is outside of the realm of possibility for Go. It's just that the standard library authors saw fit not to pursue that avenue.

This variability is honestly one of the reasons why I dislike interviews that require me to synthesize solutions to toy problems in a very tightly constrained window of time, particularly if the recruiter makes me commit at the outset to one language over another as part of the overall interview process. It's frustrating for me, and, having been on the other side, it's noisy for the interviewer.

(In fact, my favorite interview loop of all time required that I use gdb to dig into a diabolical system that was crashing, along with some serious code spelunking. The rationale was that, if I'm good with a debugger and adept at reading the source that's in front of me, the final third of synthesizing code solutions to problems and conforming to institutional practice can be dealt with once I'm in the door.)