How to handle a Signal in Go

Use the GetSignalChannel() API from the go.temporal.io/sdk/workflow package to get the Signal Channel. Get a new Selector and pass it the Signal Channel and a callback function to handle the payload.

func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) error {
  // ...
  var signal MySignal
  signalChan := workflow.GetSignalChannel(ctx, "your-signal-name")
  selector := workflow.NewSelector(ctx)
  selector.AddReceive(signalChan, func(channel workflow.ReceiveChannel, more bool) {
      channel.Receive(ctx, &signal)
      // ...
  })
  selector.Select(ctx)
  if len(signal.Message) > 0 && signal.Message != "SOME_VALUE" {
      return errors.New("signal")
  }
  // ...
}

In the example above, the Workflow code uses workflow.GetSignalChannel to open a workflow.Channel for the Signal type (identified by the Signal name). We then use a workflow.Selector and the AddReceive() to wait on a Signal from this channel. The more bool in the callback function indicates that channel is not closed and more deliveries are possible.

Before completing the Workflow or using Continue-As-New, make sure to do an asynchronous drain on the Signal channel. Otherwise, the Signals will be lost.