I was seeing the following warning when I did using StorageIntegration (a package I was developing):
StorageIntegration Waiting for background task / IO / timer.
[pid 36551] waiting for IO to finish:
Handle type uv_handle_t->data
This means that a package has started a background task or event source that has not finished running. For precompilation to complete successfully, the event source needs to be closed explicitly. See the developer documentation on fixing precompilation hangs for more help.
I think this warning could be improved by pointing at the exact documentation on how to fix it: E.g. docs.julialan.org/en/v1/devdocs/precompile_hang/
The warning coujld also be improved by mentioning that the problem is that some __init__() function in StorageIntegration or one of the packages it depends on is failing to wait for something to complete. It may be spawning a task, for example. The fix is usually for __init__ to wait for that something to complete.