WIP: Fix UNIX sockets not working when HTTP proxy defined
As mentioned in https://github.com/grpc/grpc-go/issues/2510#issuecomment-445389118, gprc-go currently does not natively support dialing a UNIX socket. The workaround is to use the passthrough resolver as suggested in https://github.com/grpc/grpc-go/issues/1846#issuecomment-362634790.
Closes #1447 (closed)
Edited by Stan Hu