config package code refactor

server/config/parser.go

@@ -7,8 +7,6 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
-var lock sync.Mutex
-
 type Config struct {
 	Port            int    `yaml:"port"`
 	DownloadPath    string `yaml:"downloadPath"`
@@ -20,6 +18,20 @@ type Config struct {
 	SessionFilePath string `yaml:"session_file_path"`
 }
 
+var (
+	instance     *Config
+	instanceOnce sync.Once
+)
+
+func Instance() *Config {
+	if instance == nil {
+		instanceOnce.Do(func() {
+			instance = &Config{}
+		})
+	}
+	return instance
+}
+
 func (c *Config) LoadFile(filename string) error {
 	fd, err := os.Open(filename)
 	if err != nil {
@@ -32,16 +44,3 @@ func (c *Config) LoadFile(filename string) error {
 
 	return nil
 }
-
-var instance *Config
-
-func Instance() *Config {
-	if instance == nil {
-		lock.Lock()
-		defer lock.Unlock()
-		if instance == nil {
-			instance = &Config{}
-		}
-	}
-	return instance
-}