fix golint issues in core/logx (#496)

core/logx/lesslogger.go

@@ -1,21 +1,25 @@
 package logx
 
+// A LessLogger is a logger that control to log once during the given duration.
 type LessLogger struct {
 	*limitedExecutor
 }
 
+// NewLessLogger returns a LessLogger.
 func NewLessLogger(milliseconds int) *LessLogger {
 	return &LessLogger{
 		limitedExecutor: newLimitedExecutor(milliseconds),
 	}
 }
 
+// Error logs v into error log or discard it if more than once in the given duration.
 func (logger *LessLogger) Error(v ...interface{}) {
 	logger.logOrDiscard(func() {
 		Error(v...)
 	})
 }
 
+// Errorf logs v with format into error log or discard it if more than once in the given duration.
 func (logger *LessLogger) Errorf(format string, v ...interface{}) {
 	logger.logOrDiscard(func() {
 		Errorf(format, v...)