Go library for timing things and yielding rates, percentiles, and histograms

 Tachymeter captures event timings and returns latency and rate
 statistics, making it possible to answer questions like: “In a loop
 with 1000 database calls, what was the 95th percentile and the lowest
 observed latency? What was the per-second rate?”
 .
 Tachymeter stores data in a lossless sliding window. This means it's
 accurate but takes space, linearly proportional to the desired sample
 size.