code: func WithValue(parent Context, key interface{}, val interface{}) Context {
  	internalCtx, ok := parent.(context.Context)
  	if !ok {
  		panic(stderrs.New("Invalid context type"))
  	}
  	return context.WithValue(internalCtx, key, val)
  }
docs: // WithValue returns a copy of parent in which the value associated with key is val.