Create example of generating a go client

Author: laduke

examples/go/README.md

@@ -0,0 +1,12 @@
+# golang client example
+
+``` sh
+go generate
+go run main.go
+```
+
+This example uses https://github.com/oapi-codegen/oapi-codegen to generate a golang client from the spec. 
+There may be other generators out there that you prefer to use. 
+
+The example starts an instance of zerotier-one in a docker container and then queries it with the generated client. 
+