Actors in Go: How lockstep Runs One Actor in Your Program and in Tests

Description and use

The article demonstrates implementing an actor model in Go using lockstep: typed messages, bounded mailboxes, non-blocking effects, and deterministic testing.

Problem

Implementing actor semantics in Go without a dedicated runtime, managing state, bounded mailboxes, and non-blocking I/O.

Outcome

The shop actor correctly reserves stock before charging, uses lockstep.Do for non-blocking I/O, and runs deterministically in tests.

Workflow

• Define message types and actor struct
• Implement Receive to handle Buy, charged, and Sold messages
• Use lockstep.Spawn to create actor and obtain typed PID
• Send Buy messages to actor; lockstep.Do starts Charge effect
• Handle charged result in a later turn
• Reply with Sold message via ReplyTo
• Run same code under go test with deterministic seed

Evidence

lockstep runs them in your program on a pool of worker goroutines.

Source

The same actor code also runs in go test, in a simulation with its own clock and network.

Source

lockstep.Do starts an effect and returns at once.

Source