You need to setup protoc to build.
brew install protobuf
sudo pacman -S protobuf
then run this:
go get -v google.golang.org/protobuf/cmd/protoc-gen-go google.golang.org/grpc/cmd/protoc-gen-go-grpc
and put your certs to certs/{cert.pem,privkey.pem}.
grpc-web needs to run with this proxy and also needs these certs for TLS.
Just run make run. It requires that certs file (cert.pem, privkey.pem) in /certs/ folder
After that, you can access on port 4000.