GitHub Actions parallel steps

Steps can run concurrently within one job, with separate logs and execution:

• background: true: starts a step asynchronously; execution proceeds immediately.
• wait: blocks until specific named background steps finish.
• wait-all: blocks until all earlier background steps finish.
• cancel: gracefully stops a background step, including a long-running service.
• parallel: groups concurrent steps and waits for the group to finish; shorthand for background steps followed by a wait.

Reference: workflow syntax.