package main

import (
	"github.com/gin-gonic/gin"
)

type TestStrErr string

func (e TestStrErr) Error() string { return string(e) }

func main() {
	testErr := TestStrErr("some error")

	err := &gin.Error{Err: testErr}

	if errors.Is(err, testErr) {
	    fmt.Println("match with testErr ok")
	}
	
	var unwrap TestStrErr
	if errors.As(err, &unwrap) {
	    fmt.Println("succesfully unwrapped as a TestStrErr")
	}
}

match with testErr ok
succesfully unwrapped as a TestStrErr