I expect following code to print the wrapped error in both pointer and non-pointer uses. But it prints nil when you use it without pointer

package main

import (
	"errors"
	"fmt"

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

func main() {
	err := gin.Error{Err: errors.New("test error")}
	fmt.Println(errors.Unwrap(err))  // prints nil
	fmt.Println(errors.Unwrap(&err)) // prints "test error" correctly
}

#631 removed pointer from Error() receiver to make gin.Error usable without pointer but the same change needs to be done for Unwrap() method as well