package main

import (
	"flag"
	"fmt"
)

var (
	volumeName = flag.String("name", "", "volume name")
	volumeSize = flag.String("size", "", "volume size")
)

func main() {
	flag.Parse()
	fmt.Printf("%d, %d \n\n", flag.NArg(), flag.NFlag())
}

$ go run example.go arg -size
2, 0 
$ go run example.go.go -name arg -size
flag needs an argument: -size
Usage of /tmp/go-build476191376/b001/exe/example:
  -name string
    	volume name
  -size string
    	volume size
exit status 2
$ go run example.go.go -name -size arg -size
2, 1