some improvements

cloud/cloud.go

@@ -49,11 +49,11 @@ type Token struct {
 func (a *Account) loadPrivateKey() (*rsa.PrivateKey, error) {
 	data, err := os.ReadFile(a.KeyFile)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("read key file: %w", err)
 	}
 	rsaPrivateKey, err := jwt.ParseRSAPrivateKeyFromPEM(data)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("parse key file: %w", err)
 	}
 	return rsaPrivateKey, nil
 }

config/cache.go

@@ -16,7 +16,7 @@ type Cache struct {
 // readCachedToken reads cached token from file.
 func readCachedToken(fileName string) (string, error) {
 	if fileName == "" {
-		return "", nil
+		return "", nil // no file name, no cache
 	}
 	data, err := os.ReadFile(fileName)
 	if err != nil {
@@ -48,7 +48,7 @@ func readCachedToken(fileName string) (string, error) {
 // writeCachedToken writes token to a cache file.
 func writeCachedToken(fileName, token string, expiresAt time.Time) error {
 	if fileName == "" {
-		return nil // no cache
+		return nil // no file name, no cache
 	}
 
 	cache := &Cache{Token: token, Expired: expiresAt.Format(time.DateTime)}

config/config.go

@@ -64,6 +64,9 @@ func New(fileName, configDir, cacheDir string, noCache, debug bool, logger *log.
 }
 
 func (c *Config) setLogger(logger *log.Logger, debug bool) {
+	c.Lock()
+	defer c.Unlock()
+
 	if debug || c.Debug {
 		logger.SetOutput(os.Stdout)
 	}
@@ -72,6 +75,9 @@ func (c *Config) setLogger(logger *log.Logger, debug bool) {
 
 // setFiles sets paths for key file and auth cache.
 func (c *Config) setFiles(configDir, cacheDir string) error {
+	c.Lock()
+	defer c.Unlock()
+
 	if !filepath.IsAbs(c.Translation.KeyFile) {
 		c.Translation.KeyFile = filepath.Join(configDir, c.Translation.KeyFile)
 	}
@@ -102,6 +108,9 @@ func (c *Config) setFiles(configDir, cacheDir string) error {
 
 // setProxy sets HTTP proxy or uses environment variables.
 func (c *Config) setProxy() error {
+	c.Lock()
+	defer c.Unlock()
+
 	if c.ProxyURL != "" {
 		u, err := url.Parse(c.ProxyURL)