use the user's GOPROXY settings when requesting the gopls version

[stamblerre]

I think this change, in conjunction with the setting to disable gopls automatic updates might be enough to solve the issue with making requests directly.

[stamblerre]

After some discussion with teammates, this is the correct approach for the gopls automatic updates. $GOPROXY wasn't on by default when I made the original PR, which is why I had used https://proxy.golang.org directly. With Go 1.13, GOPROXY is on by default, so this should be fine. It will be used when running the go command anyway, so I think it's fine to have this as opt-out with a setting to disable.

[ramya-rao-a]

We plan to do this not more than once per each VS Code session right?
If so, then on start up, we do run go env GOPATH GOROOT.
We can append GOPROXY to that and have the value stored in process.env['GOPROXY'] and skip the below.

[ramya-rao-a]

I believe re-using that go env call is a good move. If you agree, you can cherry pick this commit of mine

[stamblerre]

Done, thanks!