Unmanned Aerial Vehicles (UAVs), also called drones, are getting a lot of attention in various application scenarios such as search and rescue missions, infrastructure inspections, and delivery system. In addition, it is of increasing interest to researchers, which a group of drones are networked and coordinated to accomplish a mission delivered from Ground Control Station (GCS). To support those service scenarios, communication path should be maintained between GCS and the UAVs, and the UAVs should be able to exchange a message among themselves. However, communication range between GCS and the UAVs is bounded according to the transceiver power and its sensitivity. Hence, a multihop network approach need to be considered. In such multihop networks, routing protocol plays an important role. Accordingly, in this paper, we present a geolocation-based routing protocol for Flying Ad hoc Networks (FANETs) with multihop network communication. Our protocol shows robust and resilient performance to the dynamic multihop network topology. A network topology composed of UAVs is highly dynamic due to the high speed of UAVs while executing missions. In this circumstance, our protocol uses geolocation information of neighbors and then find the routing path to the destination by only considering the neighbor information, which in turn, results in low overhead and robustness to the dynamic network topology in FANETs. We also provide implementation of the proposed geolocation-based routing protocol and testbed environments.