[Go] Working on a go example plus fixing go grpc code (#6448)

Implemented server.go and half implemented client.go

Finishes implementation for greeter go example

Update grpc code for monster.fbs

Adds a couple of cpp methods

Adhere to gofmt standards

Adds a readme for issues with grpc

.gitignore

@@ -140,4 +140,6 @@ yarn-error.log
 .cache/
 /flatbuffers.lib
 .cmake/
-**/dist
+**/dist
+**/vendor
+**/go.sum