improve chrome web store XML parsing

extver.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"encoding/xml"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -15,6 +16,10 @@ var (
 	defaultProdVersion = "113.0"
 )
 
+var (
+	ErrNoVerData = errors.New("no version data returned")
+)
+
 type StoreExtUpdateResponse struct {
 	XMLName xml.Name `xml:"gupdate"`
 	App     *struct {
@@ -85,7 +90,7 @@ func GetExtVer(ctx context.Context,
 	}
 
 	reader := io.LimitReader(resp.Body, 64*1024)
-	var respData StoreExtUpdateResponse
+	var respData *StoreExtUpdateResponse
 
 	dec := xml.NewDecoder(reader)
 	err = dec.Decode(&respData)
@@ -93,5 +98,10 @@ func GetExtVer(ctx context.Context,
 		return "", fmt.Errorf("unmarshaling of chrome web store response failed: %w", err)
 	}
 
-	return respData.App.UpdateCheck.Version, nil
+	if respData != nil && respData.App != nil &&
+		respData.App.UpdateCheck != nil && respData.App.UpdateCheck.Version != "" {
+		return respData.App.UpdateCheck.Version, nil
+	}
+
+	return "", ErrNoVerData
 }

main.go

@@ -183,7 +183,7 @@ func run() int {
 		defer cl()
 		extVer, err := GetExtVer(ctx, nil, HolaExtStoreID, dialer)
 		if err != nil {
-			mainLogger.Critical("Can't detect latest API version. Try to specify -ext-ver parameter")
+			mainLogger.Critical("Can't detect latest API version. Try to specify -ext-ver parameter. Error: %v", err)
 			return 8
 		}
 		args.extVer = extVer