code: func (ctx *RequestCtx) SetUserValue(key string, value interface{}) {
  	ctx.userValues.Set(key, value)
  }
docs: // SetUserValue stores the given value (arbitrary object)
  // under the given key in ctx.
  //
  // The value stored in ctx may be obtained by UserValue*.
  //
  // This functionality may be useful for passing arbitrary values between
  // functions involved in request processing.
  //
  // All the values are removed from ctx after returning from the top
  // RequestHandler. Additionally, Close method is called on each value
  // implementing io.Closer before removing the value from ctx.