code: func (c *Container) StopSignal() syscall.Signal {
  	if c.stopSignal == "" {
  		return defaultStopSignalInt
  	}
  	cleanSignal := strings.TrimPrefix(strings.ToUpper(c.stopSignal), "SIG")
  	sig, ok := signal.SignalMap[cleanSignal]
  	if !ok {
  		return defaultStopSignalInt
  	}
  	return sig
  }
docs: // StopSignal returns the container's own stop signal configured from
  // the image configuration or the default one.