ESS’s REPL isn’t fully functional Julia REPL and so it doesn’t recognize ] input. You can:
Use additional terminal to run Julia REPL outside of Emacs. Given that you manage packages relatively rarely, it’s not a big issue. I personally use this method.
Use julia-mode, which incorporates real Julia REPL instead of comint.
Thanks!
I do have the latest julia-mode from elpa julia-mode-20180816.2117. M-x run-julia gives the same result though as I got running julia via ESS:
┌ Warning: Terminal not fully functional
└ @ Base client.jl:342
julia> ]
ERROR: syntax: unexpected “]”
For now, just running the old fashioned way ‘using Pkg’ as you suggest seems fine.