Agreed, but even ignoring how it shines light on bugs that might otherwise go unnoticed it should have been the default if only to follow the "principle of leas

Agreed, but even ignoring how it shines light on bugs that might otherwise go unnoticed it should have been the default if only to follow the "principle of least astonishment" (which Go is generally very good about). Even knowing the reasons why this was done (which have been widely discussed for years), I still think the default should have always been to have it set to the runtime.NumCPU value and then have clear documentation on why developers might want to set it to 1 in your own program.