[zlynx]

Goroutines had excellent context switching back when Go preferred to run in a single thread. Version 1.3 or so?

Now that Go defaults to multiple threads it has lost all of that advantage. Goroutine switching and channel send/receive has to apply all of the locking that any multithreaded program has to use.

[rurban]

You have to use locking only with inferior frameworks, who never heard of lockless threading or non-blocking IO. Locking also makes concurrency not only slow but also unsafe.