Add grpc health check. (#304)

* Add grpc health check.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* fix missing package.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* fix readme..

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* fix vet

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

rpc/example/go/send/main.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"log"
+
+	"github.com/appleboy/gorush/rpc/proto"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+const (
+	address = "localhost:9000"
+)
+
+func main() {
+	// Set up a connection to the server.
+	conn, err := grpc.Dial(address, grpc.WithInsecure())
+	if err != nil {
+		log.Fatalf("did not connect: %v", err)
+	}
+	defer conn.Close()
+	c := proto.NewGorushClient(conn)
+
+	r, err := c.Send(context.Background(), &proto.NotificationRequest{
+		Platform: 2,
+		Tokens:   []string{"1234567890"},
+		Message:  "test message",
+	})
+	if err != nil {
+		log.Fatalf("could not greet: %v", err)
+	}
+	log.Printf("Success: %t\n", r.Success)
+	log.Printf("Count: %d\n", r.Counts)
+}