Gps Time in Nanoseconds

Hello everyone,
We’re trying to implement TDoA Algorithm with Rak2245. And we noticed gps time format is in microseconds.
Is there any way to get gps time in nanoseconds? And if we can get nanoseconds then what would be accuracy of gps time?
*We’re using Semctech lora packet forwarder (https://github.com/Lora-net/packet_forwarder)

In sx1301 datasheet(https://www.semtech.com/uploads/documents/sx1301.pdf), at page 17 table 7 there is definition of timestamp step is 1 us. Also “https://github.com/Lora-net/packet_forwarder” at “v1.2.0 - 2014-02-03” topic there is “Feature: added a GPS-enabled packet forwarder, used to timestamp received packet with a globally-synchronous microsecond-accurate timestamp.” and there isn’t an update for gps time after this version.
So we cant get gps time nanosecond-level with rak2245 and semtech packet forwarder.
Thank your for fast answering