I did some reading on this a while back when I was getting started with Go. According to this link, http://peter.bourgon.org/go-in-production/, they recommend using CLI flags (parameters) instead of environment vars - they even convert environment vars to flags to their CLI apps.
It took some getting used to; but, I really do see the advantages of going pure CLI flags between development, staging and production environments - having specific scripts for each environment.
For example, here's a little web app I wrote recently:
// global flags
var isdebug bool
var port int
var cert string
var key string
var dbdsn string
var dbmaxidle int
var dbmaxopen int
var imguri string
// init is the entry point for the entire web application.
func init() {
log.Println("Starting wwwgo ...")
// setup the flags
//flag.StringVar(&host, "host", "", "Specify a host to redirect to. Use this to redirect all traffic to a single url.")
flag.IntVar(&port, "port", 8080, "Specify the port to listen to.")
flag.BoolVar(&isdebug, "isdebug", false, "Set to true to run the app in debug mode. In debug, it may panic on some errors.")
flag.StringVar(&cert, "cert", "", "Enables listening on 443 with -cert and -key files specified. This must be a full path to the certificate .pem file. See http://golang.org/pkg/net/http/#ListenAndServeTLS for more information.")
flag.StringVar(&key, "key", "", "Enables listening on 443 with -cert and -key files specified. This must be a full path to the key .pem file. See http://golang.org/pkg/net/http/#ListenAndServeTLS for more information.")
flag.StringVar(&dbdsn, "dbdsn", "root:root@tcp(localhost:3306)/dev_db?timeout=5s&tls=false&autocommit=true", "Specifies the MySql DSN connection.")
flag.IntVar(&dbmaxidle, "dbmaxidle", 0, "Sets the database/sql MaxIdleConns.")
flag.IntVar(&dbmaxopen, "dbmaxopen", 500, "Sets the database/sql MaxOpenConns.")
flag.StringVar(&imguri, "imguri", "/cdn/uploads/", "Set this to the full base uri of all images, for example on a remote CDN server or local relative virtual directory.")
flag.Parse()
// log our flags
if isdebug != false {
log.Println("DEBUG mode enabled")
}
if cert != "" && key != "" {
log.Println("Attempting SSL binding with supplied cert and key.")
}
if dbdsn != "" {
log.Printf("Using default dbdsn: %s", dbdsn)
}
...
}
This really becomes nice in staging/production environments.
A quick ./wwwgo -h for "what the heck was that parameter?" gives you full documentation:
admin@dev01:~/code/frontend/src/wwwgo [master]$ ./wwwgo -h
Usage of ./wwwgo:
-cert="": Enables listening on 443 with -cert and -key files specified. This must be a full path to the certificate .pem file. See http://golang.org/pkg/net/http/#ListenAndServeTLS for more information.
-dbdsn="root:root@tcp(localhost:3306)/dev_db?timeout=5s&tls=false&autocommit=true": Specifies the MySql DSN connection.
-dbmaxidle=0: Sets the database/sql MaxIdleConns.
-dbmaxopen=500: Sets the database/sql MaxOpenConns.
-imguri="/cdn/uploads/": Set this to the full base uri of all images, for example on a remote CDN server or local relative virtual directory.
-isdebug=false: Set to true to run the app in debug mode. In debug, it may panic on some errors.
-key="": Enables listening on 443 with -cert and -key files specified. This must be a full path to the key .pem file. See http://golang.org/pkg/net/http/#ListenAndServeTLS for more information.
-port=8080: Specify the port to listen to.
Very nice to have many options at CLI, and no documentation required - it's built into the flags package.
You can clearly see the defaults immediately.
With this type of documentation, I tend to setup all the defaults for common "development environments" that the team uses. We all have root/root access to our local databases. We all are using port 8080 for this particular web app during development, etc. That way, you just have to run:
go build
./wwwgo
And the app runs with all defaults - defaults that are documented. In production, just override the defaults. The built-in flag parsers will panic the application if any parameters are in the wrong format, which is also very nice.
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