Add upgrade-on-continue-as-new snippet for docs

features/deployment_versioning/upgrade_on_continue_as_new/README.md

@@ -0,0 +1,17 @@
+# Upgrade on Continue-as-New
+
+This snippet demonstrates how a pinned Workflow can upgrade to a new Worker Deployment Version at Continue-as-New boundaries.
+
+## Pattern
+
+Long-running Workflows that use Continue-as-New can upgrade to newer Worker Deployment Versions without patching by:
+
+1. Checking `GetContinueAsNewSuggested()` periodically
+2. Looking for `ContinueAsNewSuggestedReasonTargetWorkerDeploymentVersionChanged`
+3. Using `ContinueAsNewVersioningBehaviorAutoUpgrade` when continuing
+
+## Use Cases
+
+- Entity Workflows running for months or years
+- Batch processing Workflows that checkpoint with Continue-as-New
+- AI agent Workflows with long sleeps waiting for user input

features/deployment_versioning/upgrade_on_continue_as_new/feature.go

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+package upgrade_on_continue_as_new
+
+import (
+	"time"
+
+	"go.temporal.io/sdk/workflow"
+)
+
+// @@@SNIPSTART upgrade-on-continue-as-new-go
+// ContinueAsNewWithVersionUpgrade demonstrates how a pinned Workflow can
+// upgrade to a new Worker Deployment Version at Continue-as-New boundaries.
+// The Workflow checks for the TARGET_WORKER_DEPLOYMENT_VERSION_CHANGED reason
+// and uses AutoUpgrade behavior to move to the new version.
+func ContinueAsNewWithVersionUpgrade(ctx workflow.Context, attempt int) (string, error) {
+	if attempt > 0 {
+		// After continuing as new, return the version
+		return "v1.0", nil
+	}
+
+	// Check continue-as-new-suggested periodically
+	for {
+		err := workflow.Sleep(ctx, 10*time.Millisecond)
+		if err != nil {
+			return "", err
+		}
+
+		if info := workflow.GetInfo(ctx); info.GetContinueAsNewSuggested() {
+			for _, reason := range info.GetContinueAsNewSuggestedReasons() {
+				if reason == workflow.ContinueAsNewSuggestedReasonTargetWorkerDeploymentVersionChanged {
+					// A new Worker Deployment Version is available
+					// Continue-as-New with upgrade to the new version
+					return "", workflow.NewContinueAsNewErrorWithOptions(
+						ctx,
+						workflow.ContinueAsNewErrorOptions{
+							InitialVersioningBehavior: workflow.ContinueAsNewVersioningBehaviorAutoUpgrade,
+						},
+						"ContinueAsNewWithVersionUpgrade",
+						attempt+1,
+					)
+				}
+			}
+		}
+	}
+}
+
+// @@@SNIPEND