preparing docker

src/db/devicemessages.js

@@ -12,10 +12,10 @@ const config = require(__dirname + '/../../config/config.json')[env];
 
 var pool  = mysql.createPool({
   connectionLimit : 20,
-  host     : config.host,
-  user     : config.username,
-  password : config.password,
-  database : config.database
+  host     : process.env.DATABASE_HOST ||  config.host ||  '127.0.0.1',
+  user     : process.env.DATABASE_USER || config.username,
+  password : process.env.DATABASE_PASS || config.password,
+  database : process.env.DATABASE_DB   || config.database
 });
 // var con = mysql.createConnection({
 //   host     : 'localhost',