[Bug]: Possible to run 2 examples simultaneously

[Malarg]

What happened?

Steps to reproduce:

1. Change code of example
2. Run it
3. Switch to another example
4. Change code
5. Run it

Expected result: First example should be canceled when switching to the second
Actual result: Fist example don't cancelled

Issue Priority

Priority: 3 (minor)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner