Simple Go Error with Stacktrace

err.go

package err

import (
	"fmt"
	"runtime/debug"
)

type Err struct {
	errorWithStack string
}

func (err Err) Error() string {
	return err.errorWithStack
}

func createError(msg string, stack []byte) error {
	return &Err{fmt.Sprintf("%s\n%s", msg, string(stack))}
}

func NewError(err interface{}) error {
	if err == nil {
		return nil
	}
	stack := debug.Stack()
	switch v := err.(type) {
	case string:
		return createError(v, stack)
	case *Err:
		return v
	case Err:
		return v
	case error:
		return createError(v.Error(), stack)
	}
	return NewError("Unrecognized error type....")
}

func NewErrorf(format string, a ...interface{}) error {
	stack := debug.Stack()
	return createError(fmt.Sprintf(format, a), stack)
}