Release date: November 2016
SizedWaitGroup has the same role and close to the same API as the Golang sync.WaitGroup but it adds a limit on the amount of goroutines started concurrently.
SizedWaitGroup is quite similar to Golang's WaitGroup but adds the principle of throttling: you can specify the maximum amount of routines to spawn concurrently.
A typical use-case would be to execute as fast as possible a set of queries but without overloading the called database.