Add async activity example

Include a very basic async activity example. This is the same example
from the samples-java repository, ported to Go.

README.md

@@ -30,6 +30,9 @@ Each sample demonstrates one feature of the SDK, together with tests.
 - [**Basic mTLS hello world**](./helloworldmtls): Simple example of a
   Workflow Definition and an Activity Definition using mTLS like Temporal Cloud.
 
+- [**Basic async activity execution**](./async-activity/): Simple example of a
+  Workflow Definition starting activities asynchronously.
+
 ### API demonstrations
 
 - **Async activity completion**: Example of
@@ -230,7 +233,6 @@ resource waiting its successful completion
 
 Mostly examples we haven't yet ported from https://github.com/temporalio/samples-java/
 
-- Async activity calling: *Example to be completed*
 - Async lambda:  *Example to be completed*
 - Periodic Workflow: Workflow that executes some logic periodically. *Example to be completed*
 - Exception propagation and wrapping: *Example to be completed*

async-activity/README.md

@@ -0,0 +1,10 @@
+### Steps to run this sample:
+1) Run a [Temporal service](https://github.com/temporalio/samples-go/tree/main/#how-to-use).
+2) Run the following command to start the worker (assuming you are in the async-activity directory)
+```
+go run ./worker/main.go
+```
+3) Run the following command to start the example
+```
+go run ./starter/main.go
+```

async-activity/starter/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"context"
+	"log"
+
+	"go.temporal.io/sdk/client"
+
+	"github.com/google/uuid"
+	asyncactivity "github.com/temporalio/samples-go/async-activity"
+)
+
+func main() {
+	// The client is a heavyweight object that should be created once per process.
+	c, err := client.Dial(client.Options{})
+	if err != nil {
+		log.Fatalln("Unable to create client", err)
+	}
+	defer c.Close()
+
+	workflowOptions := client.StartWorkflowOptions{
+		ID:        "async-activity-" + uuid.NewString(),
+		TaskQueue: "async-activity",
+	}
+
+	we, err := c.ExecuteWorkflow(context.Background(), workflowOptions, asyncactivity.AsyncActivityWorkflow, "Temporal")
+	if err != nil {
+		log.Fatalln("Unable to execute workflow", err)
+	}
+
+	log.Println("Started workflow", "WorkflowID", we.GetID(), "RunID", we.GetRunID())
+
+	// Synchronously wait for the workflow completion.
+	var result string
+	err = we.Get(context.Background(), &result)
+	if err != nil {
+		log.Fatalln("Unable get workflow result", err)
+	}
+	log.Println("Workflow result:", result)
+}

async-activity/worker/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"log"
+
+	"go.temporal.io/sdk/client"
+	"go.temporal.io/sdk/worker"
+
+	asyncactivity "github.com/temporalio/samples-go/async-activity"
+)
+
+func main() {
+	// The client and worker are heavyweight objects that should be created once per process.
+	c, err := client.Dial(client.Options{})
+	if err != nil {
+		log.Fatalln("Unable to create client", err)
+	}
+	defer c.Close()
+
+	// Useful events to look for: timestamp of ActivityTaskScheduled,
+	// ActivityTaskStarted and ActivityTaskCompleted (note that they
+	// may not be in the correct timestamp order in the event history).
+	w := worker.New(c, "async-activity", worker.Options{
+		// Set this to 1 to make the activities run one after the other (note
+		// how both are scheduled at the same time, but ActivityTaskStarted
+		// differs).
+		MaxConcurrentActivityExecutionSize: 2,
+		// Set this to 0.5 to create some delay between when activities are
+		// started. Note that in this case, the started time does not differ.
+		// Only the completed time is different.
+		WorkerActivitiesPerSecond: 2,
+	})
+
+	w.RegisterWorkflow(asyncactivity.AsyncActivityWorkflow)
+	w.RegisterActivity(asyncactivity.HelloActivity)
+	w.RegisterActivity(asyncactivity.ByeActivity)
+
+	err = w.Run(worker.InterruptCh())
+	if err != nil {
+		log.Fatalln("Unable to start worker", err)
+	}
+}

async-activity/workflow.go

@@ -0,0 +1,54 @@
+package asyncactivity
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"go.temporal.io/sdk/activity"
+	"go.temporal.io/sdk/workflow"
+)
+
+// AsyncActivityWorkflow is a workflow definition starting two activities
+// asynchronously.
+func AsyncActivityWorkflow(ctx workflow.Context, name string) (string, error) {
+	ao := workflow.ActivityOptions{
+		StartToCloseTimeout: 10 * time.Second,
+	}
+	ctx = workflow.WithActivityOptions(ctx, ao)
+
+	// Start activities asynchronously.
+	var helloResult, byeResult string
+	helloFuture := workflow.ExecuteActivity(ctx, HelloActivity, name)
+	byeFuture := workflow.ExecuteActivity(ctx, ByeActivity, name)
+
+	// This can be done alternatively by creating a workflow selector. See
+	// "pickfirst" example.
+	err := helloFuture.Get(ctx, &helloResult)
+	if err != nil {
+		return "", fmt.Errorf("hello activity error: %s", err.Error())
+	}
+	err = byeFuture.Get(ctx, &byeResult)
+	if err != nil {
+		return "", fmt.Errorf("bye activity error: %s", err.Error())
+	}
+
+	return helloResult + "\n" + byeResult, nil
+}
+
+// Each of these activities will sleep for 5 seconds, but see in the temporal
+// dashboard that they were created immediately one after the other.
+
+func HelloActivity(ctx context.Context, name string) (string, error) {
+	logger := activity.GetLogger(ctx)
+	logger.Info("Hello activity", "name", name)
+	time.Sleep(5 * time.Second)
+	return "Hello " + name + "!", nil
+}
+
+func ByeActivity(ctx context.Context, name string) (string, error) {
+	logger := activity.GetLogger(ctx)
+	logger.Info("Bye activity", "name", name)
+	time.Sleep(5 * time.Second)
+	return "Bye " + name + "!", nil
+}

async-activity/workflow_test.go

@@ -0,0 +1,29 @@
+package asyncactivity
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+	"go.temporal.io/sdk/testsuite"
+)
+
+func Test_Workflow(t *testing.T) {
+	testSuite := &testsuite.WorkflowTestSuite{}
+	env := testSuite.NewTestWorkflowEnvironment()
+	env.RegisterActivity(HelloActivity)
+	env.RegisterActivity(ByeActivity)
+
+	// Mock the activities to skip the timers (and avoid test timeout).
+	env.OnActivity(HelloActivity, mock.Anything, "Temporal").Return("Hello Temporal!", nil)
+	env.OnActivity(ByeActivity, mock.Anything, "Temporal").Return("Bye Temporal!", nil)
+
+	env.ExecuteWorkflow(AsyncActivityWorkflow, "Temporal")
+
+	require.True(t, env.IsWorkflowCompleted())
+	require.NoError(t, env.GetWorkflowError())
+
+	var result string
+	require.NoError(t, env.GetWorkflowResult(&result))
+	require.Equal(t, "Hello Temporal!\nBye Temporal!", result)
+}