opgen without arguments doesn't show usage

[dolmen]

$ go run go.1password.io/spg/cmd/[email protected]
Usage of /var/folders/7b/5rfj3bgs3tj34c6f2jy8h39w0000gn/T/go-build4052941408/b001/exe/opgen:
$ go run go.1password.io/spg/cmd/[email protected] -help
Usage of /var/folders/7b/5rfj3bgs3tj34c6f2jy8h39w0000gn/T/go-build4052941408/b001/exe/opgen:
$ go run go.1password.io/spg/cmd/[email protected] help

opgen characters [--length=<n>] [--allow=<characterclasses>]
				[--exclude=<characterclasses>] [--require=<characterclasses>]
				[--entropy]

	--length    generate a password <n> characters in length (default: 20)
	--allow     allow characters from <characterclasses> (default: all)
	--exclude   exclude all characters from <characterclasses> regardless of
					other settings (default: ambiguous)
	--require   require at least one character from <characterclasses>
					(default: none)
	--entropy   show the entropy of the password recipe

	<characterclasses>: uppercase, lowercase, digits, symbols, ambiguous

opgen words [--list=<wordlist> | --file=<wordlistfile>] [--size=<n>]
				[--separator=<separatorclass>] [--capitalize=<scheme>]
				[--entropy]

	--list         use built-in <wordlist> (default: words)
	--file         use a wordlist file at the specified path
	--size         generate a password with <n> elements (default: 4)
	--separator    separate components with <separatorclass> (default: hyphen)
	--capitalize   capitalize password according to <scheme> (default: none)
	--entropy      show the entropy of the password recipe

	<wordlist>: words, syllables
	<separatorclass>: hyphen, space, comma, period, underscore, digit, none
	capitalization <scheme>: none, first, all, random, one
	
exit status 2

Expected behavior: running the program without any argument or with any argument starting with '-' should show the full usage.