This post contains references to outdated APIs.
Please read the following for the new APIs: https://www.thethingsnetwork.org/forum/t/new-api-for-gateway-mapping-status-and-info/49778
You can get many from https://www.thethingsnetwork.org/gateway-data/ Any JSON-parser can retrieve the coordinates from this.
I think this only includes gateways for which the owners have allowed to share this data:
You can limit the output:
Also, this does not include the LoRaWAN-enabled satellites from Lacuna Space. 
(Aside: “geolocation” refers to determining the coordinates, so I’ve edited your topic’s title for future visitors. I don’t know what other options you’d expect in “the geo-locations of the gateways, preferably a list of coordinates”.)