The two examples fail to start in the containers because they are
compiled with CGO enabled requiring some dynamic standard libraries
that are not present there:
```
$ docker-compose up
...
broker-webapp_1 | /bin/sh: broker-webapp: not found
stock-quotes-service_1 | /bin/sh: stock-quotes-service: not found
...
```
This commit solves that by using CGO_ENABLED=0 to disable CGO.
Signed-off-by: Mauricio Vásquez <mauricio@accuknox.com>
Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>