code: func (ctx *RequestCtx) Value(key interface{}) interface{} {
  	if keyString, ok := key.(string); ok {
  		return ctx.UserValue(keyString)
  	}
  	return nil
  }
docs: // Value returns the value associated with this context for key, or nil
  // if no value is associated with key. Successive calls to Value with
  // the same key returns the same result.
  //
  // This method is present to make RequestCtx implement the context interface.
  // This method is the same as calling ctx.UserValue(key)