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OmniSharp failed to start in VSCode terminal when I open project for Unity.
Reinstalling or Updating Mono and .Net core was failed.
Well, OmniSharp use Mono compiler not .Net core things. So it won't be problem of .Net core.
May be terminal on VSCode has problem, like messed bash profile.
Yes. bash history showed that when I overwrite bash profile I just forget to adding $PATH on the end, ignoring default path.
I just didn't notice cause new packages on new added path works well. Fuck myself (on yesterday).
Adding $PATH, all fixed.