nanotime在MacOS上做什么？

I am currently trying to understand how nanotime is implemented for MacOS in Go.

On Linux (see link to implementation here), it seems to calls clock_gettime.

On Windows (see link to implementation here), it seems to call QueryPerformanceCounter.

But I cannot find what it does on MacOS and what kind of equivalent system function it calls. What does it do on MacOS?

Note: link to the source code are very welcome.

Here is the nanotime implementation for Darwin. It calls into nanotime_trampoline, implemented in Go assembly which in turns seems to call mach_absolute_time, defined in macOS's libSystem