go: flag: cli

[AmitKumarDas]

• refer:https://cs.opensource.google/go/x/tools/+/refs/tags/v0.22.0:cmd/gonew/main.go

• 
  func usage() {
  fmt.Fprintf(os.Stderr, "usage: gonew srcmod[@version] [dstmod [dir]]\n")
  fmt.Fprintf(os.Stderr, "See https://pkg.go.dev/golang.org/x/tools/cmd/gonew.\n")
  os.Exit(2)
  }

func main() { log.SetPrefix("gonew: ") log.SetFlags(0) flag.Usage = usage flag.Parse() args := flag.Args()

if len(args) < 1 || len(args) > 3 {
usage()
}

// more code ...

}