monotime provides a portable monotonic timer for Go / Golang.

• Linux: Uses runtime.nanotime
• Windows: Uses QueryPerformanceCounter docs
• macOS: Uses mach_absolute_time docs (requires CGO)
• FreeBSD: Uses clock_gettime(CLOCK_MONOTONIC) docs

The Go standard library provides time.Now for getting the current time, but this timestamp is not monotonic -- it can jump forward or backwards depending on the operating systems' time synchronization. The standard library does not provide a public API for getting the monotonic time from the operating system, but on some operating systems runtime.nanotime, a private method, is available, and generally is the fastest method to get a monotonic time. However, on many operating systems including macOS and Windows, runtime.nanotime doesn't actually implement a monotonic timer.

When possible this library uses runtime.nanotime, but on platforms where it is not available monotime may use other methods.

See the following golang/go issues for more background:

• #12914: runtime: time: expose monotonic clock source
• #17610: runtime: use mach_absolute_time for runtime.nanotime
• #6007: time: use monotonic time on netbsd