通过flag.PrintDefaults（）设置输出顺序

I want to make the help message by my program more clear by changing stdout output. Now I using of flag.Usage for provide of additional information but also I want to change of an order of output the flags. Now flags are sorted by alphabetical but I need to change an order to logical. E.g. Now:

./mytool --help
-aaa
  input file of aaa
-bbb 
  input file of bbb
-mode 
  job's mode

I wish :)

./mytool --help
-mode 
  job's mode
-aaa
  input file of aaa
-bbb 
  input file of bbb

Thank you so much!

According to the source code of flag, it is impossible to modify the order of flag.PrintDefault().

However, you can write a custom flag.Usage function, like the following example:

package main
import (
    "flag"
    "fmt"
)
func main() {
    flag.String("aaa", "foo", "input file of aaa")
    flag.String("bbb", "foo", "input file of aaa")
    flag.String("mode", "foo", "job's mode")

    flag.Usage = func() {
        flagSet := flag.CommandLine
        fmt.Printf("Custom Usage of %s:
", "./mytool")
        order := []string{"mode", "aaa", "bbb"}
        for _, name := range order {
            flag := flagSet.Lookup(name)
            fmt.Printf("-%s
", flag.Name)
            fmt.Printf("  %s
", flag.Usage)
        }
    }
    flag.Parse()
}

The output:

Custom Usage of ./mytool:
-mode
  job's mode
-aaa
  input file of aaa
-bbb
  input file of aaa