Channels and the goroutine scheduler need to be thread safe. They use locks and/or synchronized instructions that run much slower because they need to synchroni

Channels and the goroutine scheduler need to be thread safe. They use locks and/or synchronized instructions that run much slower because they need to synchronize between the different cores of your CPU (or between CPUs, if you have more than one, which is slower still.) Running goroutines also saves and restores registers, trash part of the cache, or move to another core with a cold cache. Threads have more overhead, and processes more still, but that still is very slow.