func GetString(v interface{}) string {
	switch result := v.(type) {
	case string:
		return result
	case []byte:
		return string(result)
	default:
		if v != nil {
			return fmt.Sprintf("%v", result)
		}
	}
	return ""
}
convert interface to string.
package cache
import (
	"fmt"
	"strconv"
)