I assume you're calling the go command a few times in parallel, hence the improvement with -j4. I wonder if it would be faster to aggregate all the packages you need to build in a variable, and call the go command with all of them.
i.e. instead of issuing "go build foo/mylib" and "go build bar/myotherlib" in parallel, just issuing "go build foo/mylib bar/myotherlib".
I say this because I remember there being logic inside the go command to parallelize builds already, see the "-p" flag in "go help build". In particular, the go command will be able to avoid statting all the files, comparing mod times twice, recomputing the DAG, etc. Although, considering how fast it runs anyway, this speedup might be negligible...
i.e. instead of issuing "go build foo/mylib" and "go build bar/myotherlib" in parallel, just issuing "go build foo/mylib bar/myotherlib".
I say this because I remember there being logic inside the go command to parallelize builds already, see the "-p" flag in "go help build". In particular, the go command will be able to avoid statting all the files, comparing mod times twice, recomputing the DAG, etc. Although, considering how fast it runs anyway, this speedup might be negligible...