The primary online discussion venue for Julia is the Discourse forum. Discourse is the right place to do any of the following:

For Chinese users a Simplified Chinese version discourse is also hosted by the community. Please click this Julia中文论坛 link.

The Discourse forum replaced the Julia mailing lists, the largest of which were julia-users and julia-dev, at the end of 2016. Those lists are now read-only but you may like to search them to see if your question has already been raised.