run docker with yaml config file (#207)

Author: TimothyYe

README.md

@@ -1013,6 +1013,17 @@ docker run \
 timothyye/godns:latest
 ```
 
+To run it with a `YAML` config file:
+
+```bash
+docker run \
+-d --name godns \
+-e CONFIG=/config.yaml \
+--restart=always \
+-v /path/to/config.yaml:/config.yaml \
+timothyye/godns:latest
+```
+
 ### As a Windows service
 
 1. Download the latest version of [NSSM](https://nssm.cc/download)

cmd/godns/godns.go

@@ -14,6 +14,10 @@ import (
 	"github.com/fatih/color"
 )
 
+const (
+	configEnv = "CONFIG"
+)
+
 var (
 	configuration settings.Settings
 	optConf       = flag.String("c", "./config.json", "Specify a config file")
@@ -28,15 +32,24 @@ func init() {
 }
 
 func main() {
+
 	flag.Parse()
 	if *optHelp {
 		color.Cyan(utils.Logo, Version)
 		flag.Usage()
 		return
 	}
 
+	configPath := *optConf
+
+	// read config path from the environment
+	if os.Getenv(configEnv) != "" {
+		// overwrite the config path
+		configPath = os.Getenv(configEnv)
+	}
+
 	// Load settings from configurations file
-	if err := settings.LoadSettings(*optConf, &configuration); err != nil {
+	if err := settings.LoadSettings(configPath, &configuration); err != nil {
 		log.Fatal(err)
 	}