如何在Golang urfave CLI中将标志值传递给子命令

I am using urfave at https://github.com/urfave/cli to create a CLI with two subcommands. I am able to create a CLI with a subcommand, but I really have no idea how to define the flags. What's the difference between the global flag and local flag?

Each command can optionally specify a 'subcommand'. The subcommand is of type Command, which allows for nested / composing commands together.

To achieve something like:

cli-tool command1 command2 --command2flag

you could have a commands structure like:

app := &cli.App{
    //...
    Commands: []*cli.Command{
      {
        Name:    "command1",
        Usage:   // ...
        Action:  //...
        SubCommand: []cli.Command{
           {
               Name: "command2"
               Flags: []cli.Flag{
                  cli.StringFlag{
                     Name: "command2flag"
                     // ...
                  },
               },
           },
        },
      },
    //...
    }

You can see here that command2 is nested in command1's subcommands. And the flags for command2 will only apply to command2. This is an example of a local flag.

Global flags would apply to every command and subcommand. This could be useful for somekind of config that the cli tool might need to use for all commands. e.g. the server address to talk to etc.