server hang using tasks

Stream: lean4

[Mario Carneiro]

This code causes the vscode server to hang for me:

#eval show IO Unit from do
  let t ← IO.asTask (IO.println "hi")
  _ ← IO.wait t

It works fine in the console.

[Sebastian Ullrich]

Thanks for the reminder, this is https://github.com/leanprover/lean4/issues/426