Install using Homebrew

brew tap lanterndata/lantern
brew install lantern && lantern_install

CREATE EXTENSION lantern;
CREATE TABLE lantern_demo (id SERIAL, v REAL[3]);
INSERT INTO lantern_demo (v) VALUES ('{0, 0, 0}'), ('{0, 1, 0}'), ('{1, 0, 0}');
CREATE INDEX ON lantern_demo USING hnsw(v) WITH (m=4, ef_construction=8);
SET enable_seqscan=off; -- to always use index on scan
SELECT * FROM lantern_demo ORDER BY v <-> ARRAY[1,1,1];