BuntDB
Database for Go with custom indexing and geospatial support
...Among its distinguishing features are support for custom indexing (even within JSON values), spatial (geospatial) indexes with support up to 20 dimensions, flexible iteration over keys (ascending, descending, ranges), TTL/expiry eviction, and embeddability. Because it keeps its data in memory (with persistent backing), it's well suited for caching, session stores, small-scale databases inside Go applications, or applications that prefer simplicity and speed over massive scale. The API is simple, and the library is easy to embed into Go apps.