"Unknown arguments supplied" when the subcommand and flag have same shortname

// example.go
package main

import (
	"fmt"

	"github.com/integrii/flaggy"
)

func main() {
	subcmd := flaggy.NewSubcommand("testSubCmd")
	subcmd.ShortName = `t`
	var test string
	subcmd.String(&test, "t", "testFlag", "test flag")
	flaggy.AttachSubcommand(subcmd, 1)
	flaggy.Parse()
	fmt.Println(test)
}

go run example.go t -t hello
testSubCmd

Flags:
--version Displays the program version string.
-h --help Displays help with available flag, subcommand, and positional value parameters.
-t --testFlag test flag

Unknown arguments supplied: hello
exit status 2