Ask HN: Golang :how do i handle index out of range error?

I am writing a CLI interface program in Go.my program requires a user to enter a filename as an argument . following is the code I wrote to handle the situations in which user doesn't enter any argument . but it panics and gives an error "index out of range".how do I handle this?

if len(os.Args) == 0 { fmt.Println("usage: gohex <filename>")

        os.Exit(1)
    }