Thank you! There are two pieces of motivation here. The first one is removing boilerplate of spawning goroutines that read from one channel and write to another. Such code also needs wait/err group to properly close the output channel. I wanted to abstract this away as "channel transformation" with user controlled concurrency.

Another part is to provide solutions for some real problems I had. Most notably batching, error handling (in multi stage pipelines) and order preservation. I thought that they are generic enough to be the part of general purpose library.