code: func (m *Message) CommandArguments() string {
  	if !m.IsCommand() {
  		return ""
  	}
  
  	// IsCommand() checks that the message begins with a bot_command entity
  	entity := (*m.Entities)[0]
  	if len(m.Text) == entity.Length {
  		return "" // The command makes up the whole message
  	}
  
  	return m.Text[entity.Length+1:]
  }
docs: // CommandArguments checks if the message was a command and if it was,
  // returns all text after the command name. If the Message was not a
  // command, it returns an empty string.
  //
  // Note: The first character after the command name is omitted:
  // - "/foo bar baz" yields "bar baz", not " bar baz"
  // - "/foo-bar baz" yields "bar baz", too
  // Even though the latter is not a command conforming to the spec, the API
  // marks "/foo" as command entity.