add help to flag set

flag.go

@@ -139,6 +139,10 @@ func NewFVSet(v interface{}) (*FVSet, error) {
 			}
 		}
 	}
+	flags.BoolFunc("help", "Show help", func(s string) error {
+		flags.Usage()
+		return nil
+	})
 	return &FVSet{
 		Name:  name,
 		Value: &v,

go.mod

@@ -0,0 +1,3 @@
+module git.pyer.club/kingecg/command
+
+go 1.23.1

test/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.pyer.club/kingecg/command"
+)
+
+func main() {
+	type targs struct {
+		Test     string `flag_default:"test" flag_usage:"this is test"`
+		TestBool bool   `flag_short:"b"`
+		TestInt  int
+	}
+	sargs := &targs{}
+	v, _ := command.NewFVSet(sargs)
+	v.Parse(os.Args[1:])
+	fmt.Println(sargs)
+}