Running `go vet ./...` with `go 1.7.3` would report the following:
```
server/route.go:342: assignment copies lock value to tlsConfig: crypto/tls.Config contains sync.Once contains sync.Mutex
server/server.go:479: assignment copies lock value to config: crypto/tls.Config contains sync.Once contains sync.Mutex
```
Add a “clone” function while waiting for this to be addressed
by the language itself (https://go-review.googlesource.com/#/c/28075/)
