# Error handling

An activity, or child workflow, might fail and you could handle errors differently based on different error cases. If the activity returns an error as errors.New() or fmt.Errorf(), those errors will be converted to workflow.GenericError. If the activity returns an error as cadence.NewCustomError(“err-reason”, details), that error will be converted to *cadence.CustomError. There are other types of errors such as workflow.TimeoutError, workflow.CanceledError and workflow.PanicError. Following is an example of what your error code might look like:

err := workflow.ExecuteActivity(ctx, YourActivityFunc).Get(ctx, nil)
switch err := err.(type) {
    case *cadence.CustomError:
        switch err.Reason() {
            case "err-reason-a":
                // Handle error-reason-a.
                var details YourErrorDetailsType
                // Deal with details.
            case "err-reason-b":
                // Handle error-reason-b.
                // Handle all other error reasons.
    case *workflow.GenericError:
        switch err.Error() {
            case "err-msg-1":
                // Handle error with message "err-msg-1".
            case "err-msg-2":
                // Handle error with message "err-msg-2".
                // Handle all other generic errors.
    case *workflow.TimeoutError:
        switch err.TimeoutType() {
            case shared.TimeoutTypeScheduleToStart:
                // Handle ScheduleToStart timeout.
            case shared.TimeoutTypeStartToClose:
                // Handle StartToClose timeout.
            case shared.TimeoutTypeHeartbeat:
                // Handle heartbeat timeout.
    case *workflow.PanicError:
        // Handle panic error.
    case *cadence.CanceledError:
        // Handle canceled error.
        // All other cases (ideally, this should not happen).