$ openssl genrsa -out server.key 2048
$ openssl req -new -x509 -sha256 -key server.key -out server.crt -days 3650

$ go get -u github.com/golang/protobuf/protoc-gen-go

$ protoc -I helloworld/ helloworld/helloworld.proto --go_out=plugins=grpc:helloworld