Merge upstream/master: idiomatic Go, IP priority, flaky test fixes
Upstream changes:
- More idiomatic Golang (b6427ee)
- Change IP address set priority (1fcec38)
- Flaky CI test fixes (eedee63, 73c6a3a, e54d9d6)
Conflicts resolved:
- README.md: keep fork version
- default.pgo: removed (causes SEGV in fork builds)
- proxy.go: keep fork's counting conn, use upstream's tracker
- proxy_opts.go: keep fork's APIBindTo field