命令行解析cobra使用

package main
import (
    "fmt"
    "os"
    "github.com/spf13/cobra"
)
var RootCmd = &cobra.Command{
    Use:   "hugo",
    Short: "Hugo is a very fast static site generator",
    Long: A Fast and Flexible Static Site Generator built with</span></div><div class="line"><span class="string">                      love by spf13 and friends in Go.</span></div><div class="line"><span class="string">                                      Complete documentation is available at http://hugo.spf13.com,
    Run: func(cmd *cobra.Command, args []string) {
        
    },
}
var param string
func () {
    RootCmd.AddCommand(startCmd)
    f := startCmd.Flags()
    f.StringVarP(&param, "param", "p", "", "Source directory to read from")
    RootCmd.AddCommand(versionCmd)
}
var versionCmd = &cobra.Command{
    Use:   "version",
    Short: "Print the version number of Hugo",
    Long:  All software has versions. This is Hugo's,
    Run: func(cmd *cobra.Command, args []string) {
        fmt.Println("Hugo Static Site Generator v0.9 -- HEAD")
    },
}
var startCmd = &cobra.Command{
    Use:   "start",
    Short: "run Hugo",
    Long:  run,
    Run: func(cmd *cobra.Command, args []string) {
        fmt.Println("param is ", param)
    },
}
func main() {
    if err := RootCmd.Execute(); err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
}