The Xiaomi Mi A1 was released back in September 2017 as Xiaomi's first Android One offering. The Android One program promises just three years of software updates, however, so the Mi A1 has finally reached the end of its official lifespan. "Official" is key, though, as life continues outside the confines of stock software.
https://www.notebookcheck.net/The-Xiaomi-Mi-A1-finally-reaches-the-end-of-its-support-lifespan-but-life-continues-thanks-to-a-wide-array-of-custom-ROMs.498401.0.html