Use Go 1.9 instead of 1.8 due to performance issue

[david50407]

According to the GitLab official blog post, How a fix in Go 1.9 sped up our Gitaly service by 30x, Gitaly (GitLab Git RPC service) with Go 1.8 uses fork for ForkExec caused child process starting with a copy of the parent processes' memory, in other words, ForkExec takes longer when the process has larger virtual memory footprint.

In Go 1.9, ForkExec switch from fork to clone(2) with CLONE_VFORK and CLONE_VM flags, or as known as posix_spawn(3), which doesn't copy parent processes' memory space and has a roughly constant time.

ref: golang/go#5838
ref: https://go-review.googlesource.com/c/go/+/37439

[solidnerd]

Hey,
it's already in there see #1479 . It will be available with the 10.4.0 release.

[solidnerd]

It can be closed now.