Go's TLS support should be greatly improved in Go 1.6 thanks to the performance work you referenced by Cloudflare. The licensing issue was resolved and the work was merged 11/10/2016[1]
While GC will always carry a cost, great improvements have been made over the last year and continues to be an area of focus for each Go release. Rick Hudson gave a nice update on Go's GC improves at GopherCon 2015 [2][3]
[1] https://go-review.googlesource.com/#/c/8968