fixed middleware implementation, added middleware tracing for easier debug

internal/common/args.go

@@ -2,9 +2,9 @@ package common
 
 import (
 	"flag"
+	"fmt"
 
 	"github.com/sirupsen/logrus"
-	E "github.com/yusing/go-proxy/internal/error"
 )
 
 type Args struct {
@@ -20,6 +20,7 @@ const (
 	CommandReload             = "reload"
 	CommandDebugListEntries   = "debug-ls-entries"
 	CommandDebugListProviders = "debug-ls-providers"
+	CommandDebugListMTrace    = "debug-ls-mtrace"
 )
 
 var ValidCommands = []string{
@@ -31,23 +32,24 @@ var ValidCommands = []string{
 	CommandReload,
 	CommandDebugListEntries,
 	CommandDebugListProviders,
+	CommandDebugListMTrace,
 }
 
 func GetArgs() Args {
 	var args Args
 	flag.Parse()
 	args.Command = flag.Arg(0)
-	if err := validateArg(args.Command); err.HasError() {
+	if err := validateArg(args.Command); err != nil {
 		logrus.Fatal(err)
 	}
 	return args
 }
 
-func validateArg(arg string) E.NestedError {
+func validateArg(arg string) error {
 	for _, v := range ValidCommands {
 		if arg == v {
 			return nil
 		}
 	}
-	return E.Invalid("argument", arg)
+	return fmt.Errorf("invalid command: %s", arg)
 }