xmlquery is a Go library for querying XML documents using XPath expressions. It provides functions to parse XML from various sources (string, file, URL, etc.), execute XPath queries, and manipulate the resulting node tree. The library features a caching mechanism for compiled XPath expressions to improve query performance and supports streaming parsing for large XML files to minimize memory usage. The architecture is modular, with separate concerns for parsing, querying, and node manipulation, and it relies on external dependencies for XPath expression handling and LRU caching.