code: func (mem *memNamedMapping) Update(name string, value interface{}) (success bool) {
  	_, found := mem.nameToIdx[name]
  	if found {
  		mem.putNameToIdxSync(name, value)
  		mem.publishUpdateToChannel(name, value)
  		return true
  	}
  	return false
  }
docs: // Update replaces metadata in existing item with <name>. If item is missing,
  // false value is returned.