https://jergoo.gitbooks.io/go-grpc-practice-guide/content/chapter3/gateway.html
etcd3 API全面升级为gRPC后，同时要提供REST API服务，维护两个版本的服务显然不太合理，所以grpc-gateway诞生了。通过protobuf的自定义option实现了一个网关，服务端同时开启gRPC和HTTP服务，HTTP服务接收客户端请求后转换为grpc请求数据，获取响应后转为json数据返回给客户端。

go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway

编译google.api

$ protoc -I . –go_out=plugins=grpc,Mgoogle/protobuf/descriptor.proto=github.com/golang/protobuf/protoc-gen-go/descriptor:. google/api/*.proto

编译hello_http.proto

$ protoc -I . –go_out=plugins=grpc,Mgoogle/api/annotations.proto=github.com/jergoo/go-grpc-example/proto/google/api:. hello_http/*.proto

编译hello_http.proto gateway

$ protoc –grpc-gateway_out=logtostderr=true:. hello_http/hello_http.proto

https://www.grpc.io/blog/coreos/
https://github.com/googleapis/googleapis

https://jergoo.gitbooks.io/go-grpc-practice-guide/content/chapter3/gateway.html

https://segmentfault.com/a/1190000008106582
https://github.com/googleapis/googleapis