Package level variable

example.go

// ...
const port = 8080
const path = "hash"
const key = "JAVA_SERVICE_HOST"

// hostName houses the package level hostname as a single instance
var hostName string

// SetHostname allows external packages to set the hostname
func SetHostname(name string) {
	hostName = name
}

// lookupHostname attempts to lookup the hostname if the variable is not set.
// If hostName is already set it will use that instance
func lookupHostname() string {
	// If the hostName is empty ...
	if hostName == "" {
		// then look it up via environment variable
		hostname, ok := os.LookupEnv(key)
		if !ok {
			// ... and kill execution if we can't get the variable
			log.Logger.Panicf("The environment variable %s must be set!", key)
		}
	}
	uri := fmt.Sprintf("http://%v:%v/%v", hostname, port, path)
	log.Logger.Infof("Using Java Hash Service at: %s", uri)
	return uri
}
// ...