Update README.md

Adding go-ehtereum project  as one of the biggest open-source projects to file

cmd/README.md

@@ -17,4 +17,4 @@ Examples:
 * https://github.com/kubernetes/kubernetes/tree/master/cmd
 * https://github.com/satellity/satellity/tree/master/cmd/satellity
 * https://github.com/dapr/dapr/tree/master/cmd
-
+* https://github.com/ethereum/go-ethereum/tree/master/cmd