docs / samples: Add an example of fetching an existing workflow instance after a starter process crash or shutdown.

[joeblubaugh]

Maybe I'm just failing to read the client code properly, but I can't figure out how to handle this scenario:

1. A client in a "starter" process creates a workflow instance and waits on it. Workers run in separate processes.
2. The starter process shuts down or crashes while the workflow is still executing.
3. The starter process is started again.

How do I retrieve an existing workflow instance so I can wait on its result? A sample or examples in the docs would be helpful.

[cschleiden]

You'd need to know the workflow instance id. Currently there is no way to query workflow instances by some criteria.

If you only ever have a single workflow you could also use a hard-coded well known instance id that the starter queries on.