I’m new to Julia and just study by reading official documents, but I do want to have some toy problems as testing. I’m wondering if there is online judgement supports Julia?
I’ve searched and found hackerrank was said to support Julia, it do support for only the solve me first problem, but other problems seems not.
After some search, there are some updates.
hackerrank do support julia, for some of their problems. For (Algorithms, DIFFICULTY Easy), it seems they do not support Julia. But for (Algorithms, DIFFICULTY Medium), there are julia support.
atcode seems support julia too, both of atcode and hackerrank suffer problem of outdated julia version.
I’m currently working through the Julia track at exercism.io. It doesn’t seem to have quite the depth challenges/topic of other challenge sites, but the breadth of language options is much wider!
julialang at codesignal (1.0) and at codewars (1.0 and 0.6 for older problems) is available and usable. enjoy it. like me… 
Among the sites mentioned in this post currently atcode.jp has the best Julia support (v1.4+) and the the best/largest content.
Additionally, the japanese site supports Octave (v5+) and Nim(v1+), beside the usual langs.