Expanding environment variables in the config file. 

The idea is to have common configuration file, which can be deployed on windows or linux. I.e.
{
  "network": {
    "servers": [ "host:port" ],
    "ssl ca": "${MY_HOME}/log-courier.crt",
    "ssl certificate": "${MY_HOME}/log-courier.crt",
    "ssl key": "${MY_HOME}/log-courier.key"
  },
  "files": [
    {
      "paths": [ 
	    "${MY_LOG_DIR}/app1/*.log",
	    "${MY_LOG_DIR}/app2/*.log"],
      "fields": { "type": "lumberjack" }
    }
  ]
}

Potentially, properties could be environment variables, os.ExpandEnv method solves the issue smoothly.

From go lang documentation:
ExpandEnv replaces ${var} or $var in the string according to the values of the current environment variables. References to undefined variables are replaced by the empty string.