install protocol buffers: https://github.com/protocolbuffers/protobuf#protocol-compiler-installation
$ brew install protobuf
This will install all main languages support, except Go, so follow these instructions for Go support https://github.com/golang/protobuf#installation
go get -u github.com/golang/protobuf/protoc-gen-go
go get -u -v github.com/golang/protobuf/proto
Then make sure your $GOBIN is in your path:
export GOPATH="$HOME/go"
export GOBIN="$GOPATH/bin"
export PATH="$GOBIN:$PATH"
(this step is optional since the generated code is shipped along in ths repository)
$./generate.sh
$ go run calculator_server/server.go
$ go run calculator_client/client.go