diff --git a/internal/dazBlog/dazBlog.go b/internal/dazBlog/dazBlog.go
index 70f1198..7497591 100644
--- a/internal/dazBlog/dazBlog.go
+++ b/internal/dazBlog/dazBlog.go
@@ -15,6 +15,8 @@ import (
 
 var cfgFile string
 
+// NewDazBlogCommand create the *cobra.Command object
+// so can use the Execute method to start
 func NewDazBlogCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		// specify the name of the command
@@ -33,9 +35,10 @@ Find more dBlog information at:
 		RunE: func(cmd *cobra.Command, args []string) error {
 			log.Init(logOptions())
 			defer log.Sync()
+
 			return run()
 		},
-		//
+		// no need to specify command line parameters
 		Args: func(cmd *cobra.Command, args []string) error {
 			for _, arg := range args {
 				if len(arg) > 0 {
@@ -47,9 +50,18 @@ Find more dBlog information at:
 		},
 	}
 
+	// The following settings make the initConfig function be called
+	// every time when the command is executed to read the configuration.
 	cobra.OnInitialize(initConfig)
 
-	cmd.PersistentFlags().StringVarP(&cfgFile, "config", "c", "", "The path to the miniblog configuration file. Empty string for no configuration file.")
+	// define custom flag and config
+
+	// cobra support persistent flag
+	// for providing options that work across all sub-commands of a command
+	cmd.PersistentFlags().StringVarP(&cfgFile, "config", "c", "", "The path to the dBlog configuration file. Empty string for no configuration file.")
+
+	// cobra supports local flag
+	// which can only be used within the command to which they are bound
 	cmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
 	return cmd
 }
diff --git a/internal/dazBlog/helper.go b/internal/dazBlog/helper.go
index 5d53afa..918070d 100644
--- a/internal/dazBlog/helper.go
+++ b/internal/dazBlog/helper.go
@@ -15,36 +15,52 @@ import (
 )
 
 const (
-	recommendedHomeDir = ".dazblog "
-	defaultConfigName  = "dazBlog.yaml"
+	// recommendedHomeDir defines the default directory for storing dBlog service configurations
+	recommendedHomeDir = ".dblog "
+	// defaultConfigName specifies the default configuration file name for dBlog service
+	defaultConfigName = "dazBlog.yaml"
 )
 
+// initConfig set the config file name to be read, env variable, and read config file content into viper
 func initConfig() {
 	if cfgFile != "" {
+		// read config file from the specified file
 		viper.SetConfigFile(cfgFile)
 	} else {
+		// search user's homedir
 		home, err := os.UserHomeDir()
+		// if failed, print 'Error: xxx' and do exit(1)
 		cobra.CheckErr(err)
 
+		// add `$HOME/<recommendedHomeDir>` into search path
 		viper.AddConfigPath(filepath.Join(home, recommendedHomeDir))
+		// add current dir into search path
 		viper.AddConfigPath(".")
+		// set the config file's type
 		viper.SetConfigType("yaml")
+		// set the config file's name
 		viper.SetConfigName(defaultConfigName)
 	}
 
+	// read matching env variable
 	viper.AutomaticEnv()
+	// set env variable's prefix
 	viper.SetEnvPrefix("MINIBLOG")
 
-	replacer := strings.NewReplacer(".", "-")
+	// Replace '.' and '-' with '_' in the key string before calling viper.Get(key).
+	replacer := strings.NewReplacer(".", "_", "-", "_")
 	viper.SetEnvKeyReplacer(replacer)
 
+	// read config file
 	if err := viper.ReadInConfig(); err != nil {
 		log.Errorw("Failed to read config file", "err", err)
 	}
 
+	// print the currently used config file
 	log.Infow("Using config file", "file", viper.ConfigFileUsed())
 }
 
+// logOptions reads log config from viper
 func logOptions() *log.Options {
 	return &log.Options{
 		DisableCaller:     viper.GetBool("log.disable-caller"),
diff --git a/internal/pkg/log/log.go b/internal/pkg/log/log.go
index d92557c..5380cdd 100644
--- a/internal/pkg/log/log.go
+++ b/internal/pkg/log/log.go
@@ -3,6 +3,7 @@
 // license that can be found in the LICENSE file. The original repo for
 // this file is https://github.com/Daz-3ux/dBlog.
 
+// Package log is a log package used by dazBlog project
 package log
 
 import (
@@ -30,6 +31,7 @@ type zapLogger struct {
 	z *zap.Logger
 }
 
+// ensure that zapLogger implements the Logger interface
 var _ Logger = (*zapLogger)(nil)
 
 var (
@@ -53,21 +55,33 @@ func NewLogger(opts *Options) *zapLogger {
 		opts = NewOptions()
 	}
 
+	// convert text-based log level, e.g. "info", to the zapcore.Level type
 	var zapLevel zapcore.Level
 	if err := zapLevel.UnmarshalText([]byte(opts.Level)); err != nil {
+		// if specify an invalid log level, use info level as default
 		zapLevel = zapcore.InfoLevel
 	}
 
+	// create a default zapcore.EncoderConfig
 	encoderConfig := zap.NewProductionEncoderConfig()
+
+	// customize the default zapcore.EncoderConfig
+	// customize MessageKey to "message" for a more explicit meaning
 	encoderConfig.MessageKey = "message"
+	// customize TimeKey to "timestamp" for a more explicit meaning
 	encoderConfig.TimeKey = "timestamp"
+	// customize Level style to Capital and Color
+	encoderConfig.EncodeLevel = zapcore.CapitalColorLevelEncoder
+	// customize Time format for improved readability
 	encoderConfig.EncodeTime = func(t time.Time, enc zapcore.PrimitiveArrayEncoder) {
 		enc.AppendString(t.Format("2006-01-02 15:04:05.000"))
 	}
+	// customize Duration format for improved precision
 	encoderConfig.EncodeDuration = func(d time.Duration, enc zapcore.PrimitiveArrayEncoder) {
 		enc.AppendFloat64(float64(d) / float64(time.Millisecond))
 	}
 
+	// cfg the config required to build a zap.Logger
 	cfg := &zap.Config{
 		DisableCaller:     opts.DisableCaller,
 		DisableStacktrace: opts.DisableStacktrace,
@@ -75,9 +89,11 @@ func NewLogger(opts *Options) *zapLogger {
 		Encoding:          opts.Format,
 		EncoderConfig:     encoderConfig,
 		OutputPaths:       opts.OutputPaths,
-		ErrorOutputPaths:  []string{"stderr"},
+		// specify the default inner error output path
+		ErrorOutputPaths: []string{"stderr"},
 	}
 
+	// use cfg to build a *zap.Logger
 	z, err := cfg.Build(zap.AddStacktrace(zap.PanicLevel), zap.AddCallerSkip(1))
 	if err != nil {
 		panic(err)
@@ -86,11 +102,14 @@ func NewLogger(opts *Options) *zapLogger {
 	// OOP: wrap the zap library in a custom struct
 	logger := &zapLogger{z: z}
 
+	// redirect the standard library's log to the zap logger
 	zap.RedirectStdLog(z)
 
 	return logger
 }
 
+// Sync flushes all buffered logs into disk
+// main function should call this function before exit
 func Sync() {
 	std.Sync()
 }
@@ -99,6 +118,7 @@ func (l *zapLogger) Sync() {
 	_ = l.z.Sync()
 }
 
+// Debugw print debug level log
 func Debugw(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Debugw(msg, keysAndValues...)
 }
@@ -107,6 +127,7 @@ func (l *zapLogger) Debugw(msg string, keysAndValues ...interface{}) {
 	l.z.Sugar().Debugw(msg, keysAndValues...)
 }
 
+// Infow print info level log
 func Infow(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Infow(msg, keysAndValues...)
 }
@@ -115,6 +136,7 @@ func (l *zapLogger) Infow(msg string, keysAndValues ...interface{}) {
 	l.z.Sugar().Infow(msg, keysAndValues...)
 }
 
+// Warnw print warn level log
 func Warnw(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Warnw(msg, keysAndValues...)
 }
@@ -123,6 +145,7 @@ func (l *zapLogger) Warnw(msg string, keysAndValues ...interface{}) {
 	l.z.Sugar().Warnw(msg, keysAndValues...)
 }
 
+// Errorw print error level log
 func Errorw(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Errorw(msg, keysAndValues...)
 }
@@ -131,6 +154,7 @@ func (l *zapLogger) Errorw(msg string, keysAndValues ...interface{}) {
 	l.z.Sugar().Errorw(msg, keysAndValues...)
 }
 
+// Panicw print panic level log
 func Panicw(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Panicw(msg, keysAndValues...)
 }
@@ -139,6 +163,7 @@ func (l *zapLogger) Panicw(msg string, keysAndValues ...interface{}) {
 	l.z.Sugar().Panicw(msg, keysAndValues...)
 }
 
+// Fatalw print fatal level log
 func Fatalw(msg string, keysAndValues ...interface{}) {
 	std.z.Sugar().Fatalw(msg, keysAndValues...)
 }
diff --git a/internal/pkg/log/options.go b/internal/pkg/log/options.go
index 443aafa..91be284 100644
--- a/internal/pkg/log/options.go
+++ b/internal/pkg/log/options.go
@@ -11,13 +11,19 @@ import (
 
 // Options the options for the logger
 type Options struct {
-	DisableCaller     bool
+	// if enabled, the log will display the file and line num of the calling log
+	DisableCaller bool
+	// if enabled, will print stack info for panic and higher log level
 	DisableStacktrace bool
-	Level             string
-	Format            string
-	OutputPaths       []string
+	// log level: debug, info , warn, error, dpanic, panic, fatal
+	Level string
+	// log format: console, json
+	Format string
+	// specify log output path
+	OutputPaths []string
 }
 
+// NewOptions creates an Options object with default parameters
 func NewOptions() *Options {
 	return &Options{
 		DisableCaller:     false,