code: func check(err error) {
  	if err != nil {
  		b := make([]byte, 2<<10)
  		b = b[:runtime.Stack(b, false)]
  		log.Printf("Unlikely error condition triggered: %v at %s", err, b)
  		panic(err)
  	}
  }
docs: // check should only be used for things which really shouldn't ever happen, but should
  // still be checked. If there is interesting logic in the 'else', then don't use this.