func (errs Errors) ToError() error {
	if len(errs) == 0 {
		return nil
	}
	if len(errs) == 1 {
		return errs[0]
	}
	return errs
}
ToError converts Errors to the error interface
returns nil if no errors are present, a single error object if only one is present
package multi
import (
	"fmt"
	"strings"
)
type Errors []error
func New(errs ...error) error {
	errors := Errors{}
	for _, err := range errs {
		if err != nil {
			errors = append(errors, err)
		}
	}
	if len(errors) == 0 {
		return nil
	}
	if len(errors) == 1 {
		return errors[0]
	}
	return errors
}
func Append(errs error, err error) error {
	m, ok := errs.(Errors)
	if !ok {
		return New(errs, err)
	}
	return append(m, err)
}