go/clientConnector: fix signal handling, non-2XX HTTP responses, redu…

…ndant body reading

This change adds proper signal handling by passing in a buffered
signal channel to signal.Notify as it mandates at https://pkg.go.dev/os/signal#Notify
It also handles non-2XX codes and reports this while printing the
content and returning.
While here also added resp.Body.Close() to avoid leaking HTTP responses.
Also removes redundant bytes.Buffer.ReadFrom, then .String() and string(newMsg)
by simply using io/ioutil.ReadAll(resp.Body) given we aren't sure which
version of Go being used but really in >=Go1.16, we can use io.ReadAll

Fixes #13
Fixes #14
Fixes #15

Signed-off-by: Emmanuel T Odeke <emmanuel@orijtech.com>

main.go

@@ -1,9 +1,9 @@
 package main
 
 import (
-	"bytes"
 	"context"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 	"os"
@@ -49,10 +49,20 @@ func (mycli *MyClient) eventHandler(evt interface{}) {
 			fmt.Println("Error making request:", err)
 			return
 		}
+
 		// Read the response
-		buf := new(bytes.Buffer)
-		buf.ReadFrom(resp.Body)
-		newMsg := buf.String()
+		newMsg, err := ioutil.ReadAll(resp.Body)
+		resp.Body.Close()
+		if err != nil {
+			fmt.Printf("Error reading response: %v\n", err)
+			return
+		}
+
+		if resp.StatusCode/100 != 2 { // If we don't encounter a 2XX status code, fail.
+			fmt.Printf("Non-2XX response: %s\nResponse body: %s\n", resp.Status, newMsg)
+			return
+		}
+
 		// encode out as a string
 		response := &waProto.Message{Conversation: proto.String(string(newMsg))}
 		fmt.Println("Response:", response)
@@ -77,6 +87,7 @@ func main() {
 	}
 	clientLog := waLog.Stdout("Client", "DEBUG", true)
 	client := whatsmeow.NewClient(deviceStore, clientLog)
+
 	// add the eventHandler
 	mycli := &MyClient{WAClient: client}
 	mycli.register()
@@ -108,9 +119,9 @@ func main() {
 	}
 
 	// Listen to Ctrl+C (you can also do something else that prevents the program from exiting)
-	c := make(chan os.Signal)
+	// Notify requires that there be enough capachttps://pkg.go.dev/os/signal#Notify
+	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
 	<-c
-
 	client.Disconnect()
 }