How to request Cancellation of a Workflow Execution in Go

Use the CancelWorkflow API to cancel a Workflow Execution using its Id.

cancellation/cancel/main.go

func main() {
    var workflowID string
    flag.StringVar(&workflowID, "wid", "workflowID-to-cancel", "workflowID of the Workflow Execution to be canceled.")
    flag.Parse()

    if workflowID == "" {
        flag.PrintDefaults()
        return
    }

    // The client is a heavyweight object that should be created once per process.
    c, err := client.Dial(client.Options{
        HostPort: client.DefaultHostPort,
    })
    if err != nil {
        log.Fatalln("Unable to create client", err)
    }
    defer c.Close()

    err = c.CancelWorkflow(context.Background(), workflowID, "")
    if err != nil {
        log.Fatalln("Unable to cancel Workflow Execution", err)
    }
    log.Println("Workflow Execution cancelled", "WorkflowID", workflowID)
}

How to clean up after a Workflow is cancelled

Workflow Definitions can be written to handle execution cancellation requests with Go's defer and the workflow.NewDisconnectedContext API. In the Workflow Definition below, there is a special Activity that handles clean up should the execution be cancelled.

cancellation/workflow.go

// YourWorkflow is a Workflow Definition that shows how it can be canceled.
func YourWorkflow(ctx workflow.Context) error {
    ao := workflow.ActivityOptions{
        StartToCloseTimeout: 30 * time.Minute,
        HeartbeatTimeout:    5 * time.Second,
        WaitForCancellation: true,
    }
    ctx = workflow.WithActivityOptions(ctx, ao)
    logger := workflow.GetLogger(ctx)
    logger.Info("cancel workflow started")
    var a *Activities // Used to call Activities by function pointer
    defer func() {
        
        if !errors.Is(ctx.Err(), workflow.ErrCanceled) {
            return
        }
        
        // When the Workflow is canceled, it has to get a new disconnected context to execute any Activities
        newCtx, _ := workflow.NewDisconnectedContext(ctx)
        err := workflow.ExecuteActivity(newCtx, a.CleanupActivity).Get(ctx, nil)
        if err != nil {
            logger.Error("CleanupActivity failed", "Error", err)
        }
    }()

    var result string
    err := workflow.ExecuteActivity(ctx, a.ActivityToBeCanceled).Get(ctx, &result)
    logger.Info(fmt.Sprintf("ActivityToBeCanceled returns %v, %v", result, err))

    err = workflow.ExecuteActivity(ctx, a.ActivityToBeSkipped).Get(ctx, nil)
    logger.Error("Error from ActivityToBeSkipped", "Error", err)

    logger.Info("Workflow Execution complete.")

    return nil
}