Sorry, I posted my first screenshot above with a pretty dull theme, so it sort of obscured my main point, which is that the Go syntax — e.g. the conditionals — is not being highlighted. You can see this in your screenshot by looking at the conditional at the bottom that’s wrapped around the <figcaption> element.
I just installed Neovim, thanks for the tip. By running nvim-from-vim I was able to use my complete vim plugin & configs as-is by only changing only one line. Thank you!
PS. how did you ID the exact file that code was from so quickly 
?