grpc: implement health check in go services (#27)

Also locked grpc-go to =1.14 exact version.
See grpc/grpc-go#2314 and grpc/grpc-go#2313 for reference

kubernetes-manifests/checkoutservice.yaml

@@ -28,13 +28,11 @@ spec:
           ports:
           - containerPort: 5050
           readinessProbe:
-            periodSeconds: 5
-            tcpSocket:
-              port: 5050
+            exec:
+              command: ["/bin/grpc_health_probe", "-addr=:5050"]
           livenessProbe:
-            periodSeconds: 5
-            tcpSocket:
-              port: 5050
+            exec:
+              command: ["/bin/grpc_health_probe", "-addr=:5050"]
           env:
           - name: PRODUCT_CATALOG_SERVICE_ADDR
             value: "productcatalogservice:3550"

kubernetes-manifests/productcatalogservice.yaml

@@ -29,13 +29,11 @@ spec:
         ports:
         - containerPort: 3550
         readinessProbe:
-          periodSeconds: 5
-          tcpSocket:
-            port: 3550
+          exec:
+            command: ["/bin/grpc_health_probe", "-addr=:3550"]
         livenessProbe:
-          periodSeconds: 5
-          tcpSocket:
-            port: 3550
+          exec:
+            command: ["/bin/grpc_health_probe", "-addr=:3550"]
         resources:
           requests:
             cpu: 100m

kubernetes-manifests/shippingservice.yaml

@@ -29,12 +29,11 @@ spec:
         - containerPort: 50051
         readinessProbe:
           periodSeconds: 5
-          tcpSocket:
-            port: 50051
+          exec:
+            command: ["/bin/grpc_health_probe", "-addr=:50051"]
         livenessProbe:
-          periodSeconds: 5
-          tcpSocket:
-            port: 50051
+          exec:
+            command: ["/bin/grpc_health_probe", "-addr=:50051"]
         resources:
           requests:
             cpu: 100m