fix wrong code sample in helloworld-go README.md (#5746)

code-samples/eventing/helloworld/helloworld-go/README.md

@@ -34,35 +34,37 @@ cd knative-docs/code-samples/eventing/helloworld/helloworld-go
    code creates a basic web server which listens on port 8080:
 
    ```go
+   package main
+   
    import (
      "context"
      "log"
+   
      cloudevents "github.com/cloudevents/sdk-go/v2"
      "github.com/google/uuid"
    )
    
-   func receive(ctx context.Context, event cloudevents.Event)( * cloudevents.Event, cloudevents.Result) {
+   func receive(ctx context.Context, event cloudevents.Event) (*cloudevents.Event, cloudevents.Result) {
      // Here is where your code to process the event will go.
      // In this example we will log the event msg
      log.Printf("Event received. \n%s\n", event)
-      data: = & HelloWorld {}
-      if err: = event.DataAs(data);
-      err != nil {
+     data := &HelloWorld{}
+     if err := event.DataAs(data); err != nil {
        log.Printf("Error while extracting cloudevent Data: %s\n", err.Error())
        return nil, cloudevents.NewHTTPResult(400, "failed to convert data: %s", err)
      }
      log.Printf("Hello World Message from received event %q", data.Msg)
+   
      // Respond with another event (optional)
      // This is optional and is intended to show how to respond back with another event after processing.
      // The response will go back into the knative eventing system just like any other event
-      newEvent: = cloudevents.NewEvent()
+     newEvent := cloudevents.NewEvent()
+     // Setting the ID here is not necessary. When using NewDefaultClient the ID is set
+     // automatically. We set the ID anyway so it appears in the log.
      newEvent.SetID(uuid.New().String())
      newEvent.SetSource("knative/eventing/samples/hello-world")
      newEvent.SetType("dev.knative.samples.hifromknative")
-      if err: = newEvent.SetData(cloudevents.ApplicationJSON, HiFromKnative {
-          Msg: "Hi from helloworld-go app!"
-      });
-      err != nil {
+     if err := newEvent.SetData(cloudevents.ApplicationJSON, HiFromKnative{Msg: "Hi from helloworld-go app!"}); err != nil {
        return nil, cloudevents.NewHTTPResult(500, "failed to set response data: %s", err)
      }
      log.Printf("Responding with event\n%s\n", newEvent)
@@ -71,7 +73,7 @@ cd knative-docs/code-samples/eventing/helloworld/helloworld-go
    
    func main() {
      log.Print("Hello world sample started.")
-      c, err: = cloudevents.NewDefaultClient()
+     c, err := cloudevents.NewDefaultClient()
      if err != nil {
        log.Fatalf("failed to create client, %v", err)
      }
@@ -88,13 +90,13 @@ cd knative-docs/code-samples/eventing/helloworld/helloworld-go
    // HelloWorld defines the Data of CloudEvent with type=dev.knative.samples.helloworld
    type HelloWorld struct {
      // Msg holds the message from the event
-       Msg string `json:"msg,omitempty,string"`
+     Msg string `json:"msg,omitempty"`
    }
    
    // HiFromKnative defines the Data of CloudEvent with type=dev.knative.samples.hifromknative
    type HiFromKnative struct {
      // Msg holds the message from the event
-       Msg string `json:"msg,omitempty,string"`
+     Msg string `json:"msg,omitempty"`
    }
    ```