Powerful Command-Line Applications in Go

Display Command-Line Tool Usage

Command-line tools should be helpful. Sometimes the user doesn’t know how to use a tool or they don’t remember all the options, so it’s helpful if your tool displays usage information.

Another benefit of using the flag package is that it provides automatic usage information if the user gives an invalid option or specifically requests help. You don’t have to do anything special to take advantage of this behavior either. Try it out by running your program with the -h option:

$ go build .
$ ./todo -h
Usage of ./todo:
  -complete int
        Item to be completed
  -list
        List all tasks
  -task string
        Task to be included in the ToDo list

You didn’t have to include the -h flag in your code; the ...