code: func Stacktrace(e error) string {
  	s := Stack(e)
  	if len(s) > 0 {
  		buf := bytes.Buffer{}
  		frames := runtime.CallersFrames(s)
  		for {
  			frame, more := frames.Next()
  			buf.WriteString(frame.Function)
  			buf.WriteString(fmt.Sprintf("\n\t%s:%d\n", frame.File, frame.Line))
  			if !more {
  				break
  			}
  
  		}
  		return buf.String()
  	}
  	return ""
  }
docs: // Stacktrace returns the error's stacktrace as a string formatted
  // the same way as golangs runtime package.
  // If e has no stacktrace, returns an empty string.