append fields

fields.go

@@ -1,6 +1,12 @@
 package log
 
 func (l myLogger) WithFields(fields Fields) Logger {
-	l.data = fields
+	if l.data != nil && len(l.data) > 0 {
+		for k, v := range fields {
+			l.data[k] = v
+		}
+	} else {
+		l.data = fields
+	}
 	return l
 }

logger_begin.go

@@ -6,6 +6,6 @@ func (l myLogger) Begin(s ...interface{}) Logger {
 	if hasLevel(l.level, logFlag) {
 		l.log(logFlag, append([]interface{}{"BEGIN"}, s...)...)
 	}
-	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: l.prefix, begin: time.Now(), level: l.level}
+	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: l.prefix, begin: time.Now(), level: l.level, data: l.data}
 	return logger
 }

logger_level.go

@@ -20,7 +20,7 @@ const (
 // Anything above 6 as level will be considered Level 6.
 // Pass 0 to output no logs.
 func (l myLogger) Level(level uint8) Logger {
-	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: l.prefix, begin: l.begin}
+	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: l.prefix, begin: l.begin, data: l.data}
 	switch level {
 	case 1:
 		logger.level = alertFlag

logger_prefix.go

@@ -11,6 +11,6 @@ func (l myLogger) Prefix(p ...string) Logger {
 	for _, prefix := range p {
 		buffer.WriteString(fmt.Sprintf("%s: ", prefix))
 	}
-	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: buffer.String()}
+	logger := myLogger{Writer: l.Writer, ErrWriter: l.ErrWriter, prefix: buffer.String(), data: l.data}
 	return logger
 }