code: func (ctx *RequestCtx) VisitUserValues(visitor func([]byte, interface{})) {
  	for i, n := 0, len(ctx.userValues); i < n; i++ {
  		kv := &ctx.userValues[i]
  		visitor(kv.key, kv.value)
  	}
  }
docs: // VisitUserValues calls visitor for each existing userValue.
  //
  // visitor must not retain references to key and value after returning.
  // Make key and/or value copies if you need storing them after returning.