Go使用命令行参数报错：flag provided but not defined: -xxxxx

flag provided but not defined: -xxxxx'

import (
	"flag"
	"fmt"
)

func main() {
	username := flag.String("username", "defaultName", "username")
    // 放在获取参数之后
	flag.Parse()
	fmt.Println("username=", *username)
}