Add --go-module-name flag to support generating Go module compatible code (#7651)

* Add --go-module-name flag to support generating code for go modules

* Rename echo example folder

* Grammar

* Update readme for go-echo example

* Update readme for go-echo example

* Re-enable go modules after test is done

examples/go-echo/README.md

@@ -0,0 +1,27 @@
+# Go Echo Example
+
+A simple example demonstrating how to send flatbuffers over the network in Go.
+
+## Generate flatbuffer code
+
+```
+flatc -g --gen-object-api --go-module-name echo hero.fbs net.fbs
+```
+
+## Running example
+
+1. Run go mod tidy to get dependencies
+```
+go mod tidy
+```
+
+2. Start a server
+```
+go run server/server.go
+```
+
+3. Run the client in another terminal
+```
+go run client/client.go
+```
+