How to execute a Side Effect in Go

Use the SideEffect function from the go.temporal.io/sdk/workflow package to execute a Side Effect directly in your Workflow.

Pass it an instance of context.Context and the function to execute.

The SideEffect API returns a Future, an instance of converter.EncodedValue.

Use the Get method on the Future to retrieve the result of the Side Effect.

Correct implementation

The following example demonstrates the correct way to use SideEffect:

encodedRandom := workflow.SideEffect(ctx, func(ctx workflow.Context) interface{} {
 return rand.Intn(100)
})

var random int
encodedRandom.Get(&random)
// ...
}

Incorrect implementation

The following example demonstrates how NOT to use SideEffect:

// Warning: This is an incorrect example.
// This code is nondeterministic.
var random int
workflow.SideEffect(func(ctx workflow.Context) interface{} {
      random = rand.Intn(100)
      return nil
})
// random will always be 0 in replay, so this code is nondeterministic.

On replay the provided function is not executed, the random number will always be 0, and the Workflow Execution could take a different path, breaking determinism.