Use environment variable in frontend

frontend/main.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+    "os"
     "flag"
     "strings"
+    "strconv"
 )
 
 var settingServers []string
@@ -12,17 +14,50 @@ var settingWhoisServer string
 var settingListen string
 
 func main() {
-    serversPtr := flag.String("servers", "", "server name prefixes, separated by comma")
-    domainPtr := flag.String("domain", "", "server name domain suffixes")
-    portPtr := flag.Int("port", 8000, "port bird-lgproxy is running on")
-    whoisPtr := flag.String("whois", "whois.verisign-grs.com", "whois server for queries")
-    listenPortPtr := flag.String("listen", ":5000", "address bird-lg is listening on")
+    serversDefault := ""
+    domainDefault := ""
+    proxyPortDefault := 8000
+    whoisDefault := "whois.verisign-grs.com"
+    listenDefault := ":5000"
+
+    if serversEnv := os.Getenv("BIRDLG_SERVERS"); serversEnv != "" {
+        serversDefault = serversEnv
+    }
+    if domainEnv := os.Getenv("BIRDLG_DOMAIN"); domainEnv != "" {
+        domainDefault = domainEnv
+    }
+    if proxyPortEnv := os.Getenv("BIRDLG_PROXY_PORT"); proxyPortEnv != "" {
+        var err error
+        proxyPortDefault, err = strconv.Atoi(proxyPortEnv)
+        if err != nil{
+            panic(err)
+        }
+    }
+    if whoisEnv := os.Getenv("BIRDLG_WHOIS"); whoisEnv != "" {
+        whoisDefault = whoisEnv
+    }
+    if listenEnv := os.Getenv("BIRDLG_LISTEN"); listenEnv != "" {
+        listenDefault = listenEnv
+    }
+
+    serversPtr := flag.String("servers", serversDefault, "server name prefixes, separated by comma")
+    domainPtr := flag.String("domain", domainDefault, "server name domain suffixes")
+    proxyPortPtr := flag.Int("proxy-port", proxyPortDefault, "port bird-lgproxy is running on")
+    whoisPtr := flag.String("whois", whoisDefault, "whois server for queries")
+    listenPtr := flag.String("listen", listenDefault, "address bird-lg is listening on")
     flag.Parse()
 
+    if *serversPtr == "" {
+        panic("no server set")
+    } else if *domainPtr == "" {
+        panic("no base domain set")
+    }
+
     settingServers = strings.Split(*serversPtr, ",")
     settingServersDomain = *domainPtr
-    settingServersPort = *portPtr
+    settingServersPort = *proxyPortPtr
     settingWhoisServer = *whoisPtr
-    settingListen = *listenPortPtr
+    settingListen = *listenPtr
+
     webServerStart()
 }