Print usage for Cobra sub-commands

cobra_subcommand_usage.go

package cmd

import (
  "fmt"
  "os"
  "text/tabwriter"

  "github.com/you/your-project/cmd/testcmd"
  "github.com/spf13/cobra"
)

var testCommand = &cobra.Command{
  Use:     "test",
  Aliases: []string{"t"},
  Short:   "Testing this, that and t'other",
  Long:    `Testing various functionality for this application.`,
  Run: func(cmd *cobra.Command, args []string) {
    
    // Usage for this command
    fmt.Printf(
      "%s\n\nUsage:\n  %s %s [subcommand]\n\nAvailable Subcommands:\n",
      cmd.Long,
      cmd.Root().Use,
      cmd.Use,
    )
    
    // List of sub-commands
    writer := tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ', 0)
    for _, command := range cmd.Commands() {
      fmt.Fprintf(writer, "  %s\t%s\n", command.Use, command.Short)
    }
    writer.Flush()

  },
}

func init() {
  rootCommand.AddCommand(testCommand)

  // Add any sub-commands under the "test" command
  testCommand.AddCommand(testcmd.ReleaseCommand)
  testCommand.AddCommand(testcmd.DeleteCommand)
}