Panic due to invalid validation struct tag

[romshark]

This isn't really a bug of yamagiconf, instead this is rather undesired behavior caused by github.com/go-playground/validator.

The following code produces a panic but it probably should return an error instead.

package main

import (
	"fmt"
	"net/url"
	"os"

	"github.com/romshark/yamagiconf"
)

const conf = `
host: https://localhost:8080/path
`

type Config struct {
	Host URL `yaml:"host" validate:"url,required"`
}

type URL struct{ URL *url.URL }

func (u *URL) UnmarshalText(t []byte) error {
	x, err := url.Parse(string(t))
	if err != nil {
		return err
	}
	u.URL = x
	return nil
}

func main() {
	var c Config
	err := yamagiconf.Load(conf, &c)
	if err != nil {
		fmt.Println("ERR:", err)
		os.Exit(1)
	}
	fmt.Println(c)
}

https://go.dev/play/p/7J_UIHUbkZC

panic: Bad field type main.URL

goroutine 1 [running]:
github.com/go-playground/validator/v10.isURL({0x104a46ba0?, 0x14000000900?})
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/baked_in.go:1494 +0x124
github.com/go-playground/validator/v10.New.wrapFunc.func3({0x104a1e0e0?, 0x104a47bf8?}, {0x104a46ba0?, 0x14000000900?})
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/baked_in.go:43 +0x34
github.com/go-playground/validator/v10.(*validate).traverseField(0x14000000900, {0x104a45aa0, 0x104bea200}, {0x104a1e160?, 0x1400015e1b0?, 0x14000159cd8?}, {0x104a1e0e0?, 0x1400015e1b0?, 0x104c1fde8?}, {0x1400001c400, ...}, ...)
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/validator.go:456 +0xd54
github.com/go-playground/validator/v10.(*validate).validateStruct(0x14000000900, {0x104a45aa0, 0x104bea200}, {0x104a1e160?, 0x1400015e1b0?, 0x1?}, {0x104a1e160?, 0x1400015e1b0?, 0x0?}, {0x104a47bf8, ...}, ...)
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/validator.go:78 +0x518
github.com/go-playground/validator/v10.(*Validate).StructCtx(0x14000178070, {0x104a45aa0, 0x104bea200}, {0x104a1e160, 0x1400015e1b0})
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/validator_instance.go:395 +0x330
github.com/go-playground/validator/v10.(*Validate).Struct(...)
        /Users/romshark/go/pkg/mod/github.com/go-playground/validator/[email protected]/validator_instance.go:368
main.main()
        /Users/romshark/Work/yamagiconf/cmd/panictest/main.go:32 +0x7c
exit status 2