Adding sample function in go template (#840)

* adding sample function in go template

* adding simple echo, using the correct signature

* fixing readme

.gitignore

@@ -7,7 +7,7 @@
 /coverage.out
 /bin
 /target
-
+.DS_Store
 node_modules
 __pycache__
 /coverage.out

templates/go/cloudevents/README.md

@@ -1,6 +1,6 @@
 # Go Cloud Events Function
 
-Welcome to your new Go Function! The boilerplate function code can be found in [`handle.go`](handle.go). This Function is meant to respond exclusively to [Cloud Events](https://cloudevents.io/), but you can remove the check for this in the function and it will respond just fine to plain vanilla incoming HTTP requests. 
+Welcome to your new Go Function! The boilerplate function code can be found in [`handle.go`](handle.go). This Function is meant to respond exclusively to [Cloud Events](https://cloudevents.io/), but you can remove the check for this in the function and it will respond just fine to plain vanilla incoming HTTP requests.
 
 ## Development
 
@@ -9,13 +9,14 @@ Develop new features by adding a test to [`handle_test.go`](handle_test.go) for
 Update the running analog of the function using the `func` CLI or client library, and it can be invoked using a manually-created CloudEvent:
 
 ```console
-curl -X POST -d '{"hello": "world"}' \
+curl -v -X POST -d 'hello' \
   -H'Content-type: application/json' \
   -H'Ce-id: 1' \
   -H'Ce-source: cloud-event-example' \
-  -H'Ce-type: dev.knative.example' \
+  -H'Ce-subject: Echo content' \
+  -H'Ce-type: MyEvent' \
   -H'Ce-specversion: 1.0' \
-  http://myFunction.example.com/
+  http://localhost:8080/
 ```
 
 For more, see [the complete documentation]('https://github.com/knative-sandbox/kn-plugin-func/tree/main/docs')

templates/go/cloudevents/handle.go

@@ -2,13 +2,16 @@ package function
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 
-	event "github.com/cloudevents/sdk-go/v2"
+	"github.com/cloudevents/sdk-go/v2/event"
+
+	cloudevents "github.com/cloudevents/sdk-go/v2"
 )
 
 // Handle an event.
-func Handle(ctx context.Context, event event.Event) error {
+func Handle(ctx context.Context, event cloudevents.Event) (*event.Event, error) {
 
 	/*
 	 * YOUR CODE HERE
@@ -16,10 +19,23 @@ func Handle(ctx context.Context, event event.Event) error {
 	 * Try running `go test`.  Add more test as you code in `handle_test.go`.
 	 */
 
-	// Example implementation:
-	fmt.Printf("%v\n", event) // print the received event to standard output
+	fmt.Printf("Incoming Event: %v\n", event) // print the received event to standard output
+	payload := ""
+	err := json.Unmarshal(event.Data(), &payload)
+	if err != nil {
+		fmt.Printf("%v\n", err)
+		return nil, err
+	}
 
-	return nil
+	payload = "echo " + payload
+	outputEvent := cloudevents.NewEvent()
+	outputEvent.SetSource("http://example.com/echo")
+	outputEvent.SetType("Echo")
+	outputEvent.SetData(cloudevents.ApplicationJSON, &payload)
+
+	fmt.Printf("Outgoing Event: %v\n", outputEvent)
+
+	return &outputEvent, nil
 }
 
 /*

templates/go/cloudevents/handle_test.go

@@ -2,8 +2,11 @@ package function
 
 import (
 	"context"
+	"encoding/json"
 	"testing"
 
+	cloudevents "github.com/cloudevents/sdk-go/v2"
+
 	"github.com/cloudevents/sdk-go/v2/event"
 )
 
@@ -12,11 +15,30 @@ func TestHandle(t *testing.T) {
 	// A minimal, but valid, event.
 	event := event.New()
 	event.SetID("TEST-EVENT-01")
-	event.SetType("com.example.event.test")
+	event.SetType("MyEvent")
 	event.SetSource("http://localhost:8080/")
-
+	event.SetSubject("Echo")
+	input := "hello"
+	event.SetData(cloudevents.ApplicationJSON, &input)
 	// Invoke the defined handler.
-	if err := Handle(context.Background(), event); err != nil {
+	ce, err := Handle(context.Background(), event)
+	if err != nil {
 		t.Fatal(err)
 	}
+
+	if ce == nil {
+		t.Errorf("The output CloudEvent cannot be nil")
+	}
+	if ce.Type() != "Echo" {
+		t.Errorf("Wrong CloudEvent Type received: %v , expected Echo", ce.Type())
+	}
+	output := ""
+	err = json.Unmarshal(ce.Data(), &output)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if output != "echo "+input {
+		t.Errorf("The expected output should be: 'echo hello and it was: %v", output)
+	}
+
 }