refactor: clean up code (#5308)

pkg/util/xlog/log_writer.go

@@ -19,7 +19,6 @@ import "strings"
 // LogWriter forwards writes to frp's logger at configurable level.
 // It is safe for concurrent use as long as the underlying Logger is thread-safe.
 type LogWriter struct {
-	xl      *Logger
 	logFunc func(string)
 }
 
@@ -31,35 +30,30 @@ func (w LogWriter) Write(p []byte) (n int, err error) {
 
 func NewTraceWriter(xl *Logger) LogWriter {
 	return LogWriter{
-		xl:      xl,
 		logFunc: func(msg string) { xl.Tracef("%s", msg) },
 	}
 }
 
 func NewDebugWriter(xl *Logger) LogWriter {
 	return LogWriter{
-		xl:      xl,
 		logFunc: func(msg string) { xl.Debugf("%s", msg) },
 	}
 }
 
 func NewInfoWriter(xl *Logger) LogWriter {
 	return LogWriter{
-		xl:      xl,
 		logFunc: func(msg string) { xl.Infof("%s", msg) },
 	}
 }
 
 func NewWarnWriter(xl *Logger) LogWriter {
 	return LogWriter{
-		xl:      xl,
 		logFunc: func(msg string) { xl.Warnf("%s", msg) },
 	}
 }
 
 func NewErrorWriter(xl *Logger) LogWriter {
 	return LogWriter{
-		xl:      xl,
 		logFunc: func(msg string) { xl.Errorf("%s", msg) },
 	}
 }