That's probably the rig index that you are using. Rig index start from 1 and if select, say, -r 4, but you only have 3 rigs in your list it will fail with that error.
I need to improve that error handling.
Oh sweet. This error occurs just by launching the program, but manually setting the rig index (in my case -r -4) the program appears to run. Will have to setup again as I purged grafana and influx already.
About hat error, theres a double square bracket at the end. Its a typo. If you delete one of them then it fixes it.
In my case that isn't the problem. I removed that when I first edited the conf, but the app still throws the error. With the double square it throws this error:
pi@raspberrypi:~/grm $ ./grm-2.1.d12
INFO: 2018/05/20 20:30:38 main.go:33: Starting rig-monitor...
INFO: 2018/05/20 20:30:38 main.go:50: Commmand line arguments: -config
INFO: 2018/05/20 20:30:38 main.go:54: No config file specified. Using default config.toml file: config.toml
INFO: 2018/05/20 20:30:38 config.go:92: Reading configuration file...
ERROR: 2018/05/20 20:30:38 config.go:100: Couldn't load config: While parsing config: (97, 2): unexpected token
Currently I'm no longer able to see any data populated to the phoenixminer dashboard in 2.1.d.12. I think it has to do somehow with being forced to launch with the -r -4 flag as I never had issues with that prior.