grpc/
├── gin
│   └── main.go
├── grpc
│   └── server.go
├── pb
│   ├── helloworld.pb.go
│   └── helloworld.proto
└── README.md

package main

import (
	"fmt"
	"log"
	"net/http"

	"github.com/gin-gonic/gin"
	pb "github.com/gin-gonic/gin/examples/grpc/pb"
	"google.golang.org/grpc"
)

func main() {
	// Set up a connection to the server.
	conn, err := grpc.Dial("localhost:50051", grpc.WithInsecure())
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	client := pb.NewGreeterClient(conn)

	// Set up a http server.
	r := gin.Default()
	r.GET("/rest/n/:name", func(c *gin.Context) {
		name := c.Param("name")

		// Contact the server and print out its response.
		req := &pb.HelloRequest{Name: name}
		res, err := client.SayHello(c, req)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{
				"error": err.Error(),
			})
			return
		}

		c.JSON(http.StatusOK, gin.H{
			"result": fmt.Sprint(res.Message),
		})
	})

	// Run http server
	if err := r.Run(":8052"); err != nil {
		log.Fatalf("could not run server: %v", err)
	}
}

package main

import (
	"log"
	"net"

	pb "github.com/gin-gonic/gin/examples/grpc/pb"
	"golang.org/x/net/context"
	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"
)

// server is used to implement helloworld.GreeterServer.
type server struct{}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}

func main() {
	lis, err := net.Listen("tcp", ":50051")
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	pb.RegisterGreeterServer(s, &server{})

	// Register reflection service on gRPC server.
	reflection.Register(s)
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

// Code generated by protoc-gen-go.
// source: helloworld.proto
// DO NOT EDIT!

/*
Package helloworld is a generated protocol buffer package.

It is generated from these files:
	helloworld.proto

It has these top-level messages:
	HelloRequest
	HelloReply
*/
package helloworld

import proto "github.com/golang/protobuf/proto"
import fmt "fmt"
import math "math"

import (
	context "golang.org/x/net/context"
	grpc "google.golang.org/grpc"
)

// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
var _ = fmt.Errorf
var _ = math.Inf

// This is a compile-time assertion to ensure that this generated file
// is compatible with the proto package it is being compiled against.
// A compilation error at this line likely means your copy of the
// proto package needs to be updated.
const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package

// The request message containing the user's name.
type HelloRequest struct {
	Name string `protobuf:"bytes,1,opt,name=name" json:"name,omitempty"`
}

func (m *HelloRequest) Reset()                    { *m = HelloRequest{} }
func (m *HelloRequest) String() string            { return proto.CompactTextString(m) }
func (*HelloRequest) ProtoMessage()               {}
func (*HelloRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }

// The response message containing the greetings
type HelloReply struct {
	Message string `protobuf:"bytes,1,opt,name=message" json:"message,omitempty"`
}

func (m *HelloReply) Reset()                    { *m = HelloReply{} }
func (m *HelloReply) String() string            { return proto.CompactTextString(m) }
func (*HelloReply) ProtoMessage()               {}
func (*HelloReply) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }

func init() {
	proto.RegisterType((*HelloRequest)(nil), "helloworld.HelloRequest")
	proto.RegisterType((*HelloReply)(nil), "helloworld.HelloReply")
}

// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn

// This is a compile-time assertion to ensure that this generated file
// is compatible with the grpc package it is being compiled against.
const _ = grpc.SupportPackageIsVersion4

// Client API for Greeter service

type GreeterClient interface {
	// Sends a greeting
	SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
}

type greeterClient struct {
	cc *grpc.ClientConn
}

func NewGreeterClient(cc *grpc.ClientConn) GreeterClient {
	return &greeterClient{cc}
}

func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
	out := new(HelloReply)
	err := grpc.Invoke(ctx, "/helloworld.Greeter/SayHello", in, out, c.cc, opts...)
	if err != nil {
		return nil, err
	}
	return out, nil
}

// Server API for Greeter service

type GreeterServer interface {
	// Sends a greeting
	SayHello(context.Context, *HelloRequest) (*HelloReply, error)
}

func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
	s.RegisterService(&_Greeter_serviceDesc, srv)
}

func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
	in := new(HelloRequest)
	if err := dec(in); err != nil {
		return nil, err
	}
	if interceptor == nil {
		return srv.(GreeterServer).SayHello(ctx, in)
	}
	info := &grpc.UnaryServerInfo{
		Server:     srv,
		FullMethod: "/helloworld.Greeter/SayHello",
	}
	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
		return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
	}
	return interceptor(ctx, in, info, handler)
}

var _Greeter_serviceDesc = grpc.ServiceDesc{
	ServiceName: "helloworld.Greeter",
	HandlerType: (*GreeterServer)(nil),
	Methods: []grpc.MethodDesc{
		{
			MethodName: "SayHello",
			Handler:    _Greeter_SayHello_Handler,
		},
	},
	Streams:  []grpc.StreamDesc{},
	Metadata: "helloworld.proto",
}

func init() { proto.RegisterFile("helloworld.proto", fileDescriptor0) }

var fileDescriptor0 = []byte{
	// 174 bytes of a gzipped FileDescriptorProto
	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0xe2, 0x12, 0xc8, 0x48, 0xcd, 0xc9,
	0xc9, 0x2f, 0xcf, 0x2f, 0xca, 0x49, 0xd1, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x42, 0x88,
	0x28, 0x29, 0x71, 0xf1, 0x78, 0x80, 0x78, 0x41, 0xa9, 0x85, 0xa5, 0xa9, 0xc5, 0x25, 0x42, 0x42,
	0x5c, 0x2c, 0x79, 0x89, 0xb9, 0xa9, 0x12, 0x8c, 0x0a, 0x8c, 0x1a, 0x9c, 0x41, 0x60, 0xb6, 0x92,
	0x1a, 0x17, 0x17, 0x54, 0x4d, 0x41, 0x4e, 0xa5, 0x90, 0x04, 0x17, 0x7b, 0x6e, 0x6a, 0x71, 0x71,
	0x62, 0x3a, 0x4c, 0x11, 0x8c, 0x6b, 0xe4, 0xc9, 0xc5, 0xee, 0x5e, 0x94, 0x9a, 0x5a, 0x92, 0x5a,
	0x24, 0x64, 0xc7, 0xc5, 0x11, 0x9c, 0x58, 0x09, 0xd6, 0x25, 0x24, 0xa1, 0x87, 0xe4, 0x02, 0x64,
	0xcb, 0xa4, 0xc4, 0xb0, 0xc8, 0x00, 0xad, 0x50, 0x62, 0x70, 0x32, 0xe0, 0x92, 0xce, 0xcc, 0xd7,
	0x4b, 0x2f, 0x2a, 0x48, 0xd6, 0x4b, 0xad, 0x48, 0xcc, 0x2d, 0xc8, 0x49, 0x2d, 0x46, 0x52, 0xeb,
	0xc4, 0x0f, 0x56, 0x1c, 0x0e, 0x62, 0x07, 0x80, 0xbc, 0x14, 0xc0, 0x98, 0xc4, 0x06, 0xf6, 0x9b,
	0x31, 0x20, 0x00, 0x00, 0xff, 0xff, 0x0f, 0xb7, 0xcd, 0xf2, 0xef, 0x00, 0x00, 0x00,
}

1. run grpc server

$ go run grpc/server.go

2. run gin server

$ go run gin/main.go

3. use curl command to test it

$ curl -v 'http://localhost:8052/rest/n/thinkerou'