Go's standard library doesn't provide any API to access a monotonic clock source, which means one can't reliably time how long an operation takes without copy-pasting or importing some low-level platform-dependent code such as the clock package at https://github.com/davecheney/junk.

This API doesn't necessarily need to return a time.Time, just returning a number of nanoseconds as a uint64 would be enough, kinda like Java's System.nanoTime().