これは凄いな #golang
> The directory $GOROOT/pkg no longer stores pre-compiled package archives for the standard library: go install no longer writes them, the go build no longer checks for them, and the Go distribution no longer ships them. Instead, packages in the standard library are built as needed and cached in the build cache, just like packages outside GOROOT. This change reduces the size of the Go distribution and also avoids C toolchain skew for packages that use cgo.
https://tip.golang.org/doc/go1.20