app: Use hostname instead of ip for database

app/config.template.json

@@ -23,7 +23,7 @@
     },
     "SqlSettings": {
         "DriverName": "postgres",
-        "DataSource": "postgres://mmuser:mmuser_password@PG_ADDR:PG_PORT/mattermost?sslmode=disable&connect_timeout=10",
+        "DataSource": "postgres://mmuser:mmuser_password@db:DB_PORT/mattermost?sslmode=disable&connect_timeout=10",
         "DataSourceReplicas": [],
         "MaxIdleConns": 10,
         "MaxOpenConns": 10,

app/docker-entry.sh

@@ -4,8 +4,7 @@ echo -ne "Configure database connection..."
 if [ ! -f $config ]
 then
     cp /config.template.json $config
-    sed -Ei "s/PG_ADDR/$PG_PORT_5432_TCP_ADDR/" $config
-    sed -Ei "s/PG_PORT/$PG_PORT_5432_TCP_PORT/" $config
+    sed -Ei "s/DB_PORT/$DB_PORT_5432_TCP_PORT/" $config
     echo OK
 else
     echo SKIP
@@ -13,7 +12,7 @@ fi
 
 # Wait to avoid "panic: Failed to open sql connection pq: the database system is starting up"
 echo "Wait until database is ready..."
-until nc -z $PG_PORT_5432_TCP_ADDR $PG_PORT_5432_TCP_PORT
+until nc -z db $DB_PORT_5432_TCP_PORT
 do
     sleep 1
 done