What's the best solution for communicating with ~10 people on a group project?

Not email... Slack is the obvious choice, but looking for something messaging related that's more temporary. Coordinating with a group of 10-15 people for a couple of weeks.
Niv DrorWriter/Social Editor @ProductHunt · Asked
2
JIRA Software

Omer Molad3Co-founder and CEO @ Vervoe · Written
I know this seems a bit left field compared to say Slack, but using Jira will add a lot of structure because you can assign tasks to each person. Live communication can still be facilitated using the comments function in each task. You'll know where you're up to on every tasks and be able to easily monitor progress.
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