Seconded. Load testing tools seem to either be the "hammer with a single, anonymous GET request" or jMeter which is capable of anything but painful to work with. There are some other tools out there but the lack of documentation makes it hard to tell what you can and can't do.
Drat. "Goad" -- as in the "prod" or "poke" sense of the word -- has been my defacto default name for the inevitable build script in my golang projects (once I grow out of the single-word `go` tool commands). I'll have to rename if this catches on :D
A test that would use 100 lambda functions in parallel from each of the 4 regions and run for 5 minutes would cost about 3 USD. That should achieve a concurrency level of 100,000. That would be the most expensive test possible at the moment. Smaller tests are basically free.
GitHub repo: https://github.com/gophergala2016/goad