code: func SubcommandTokenWithParams(params CommandParams) *subcommands.Command {
  	return &subcommands.Command{
  		Advanced:  params.Advanced,
  		UsageLine: params.Name,
  		ShortDesc: "prints an access token",
  		LongDesc:  "Generates an access token if requested and prints it.",
  		CommandRun: func() subcommands.CommandRun {
  			c := &tokenRun{}
  			c.params = &params
  			c.registerBaseFlags()
  			c.Flags.DurationVar(
  				&c.lifetime, "lifetime", time.Minute,
  				"Minimum token lifetime. If existing token expired and refresh token or service account is not present, returns nothing.",
  			)
  			c.Flags.StringVar(
  				&c.jsonOutput, "json-output", "",
  				"Destination file to print token and expiration time in JSON. \"-\" for standard output.")
  			return c
  		},
  	}
  }
docs: // SubcommandTokenWithParams returns subcommand.Command that can be used to
  // print current access token.