use envsubst to automatically replace env variables in the config file

.env.sample

@@ -3,6 +3,8 @@ DATABASE_PORT=5432
 REDIS_PORT=6379
 ADMINER_PORT=8080
 DATA_FOLDER=./data
+
+# Change this to your local game folder
 GAME_FOLDER=/res
 
 # Postgres specific setup

Uchu.Dockerfile

@@ -1,8 +1,8 @@
 FROM mcr.microsoft.com/dotnet/core/sdk:3.1-alpine
-ENV PATH $PATH:/root/.dotnet/tools
-
-COPY Uchu .
-COPY config.xml .
+COPY Uchu config.default.xml .env ./
 
+RUN apk add gettext
+RUN set -o allexport && source .env && set +o allexport && envsubst < config.default.xml > config.xml
 RUN dotnet build
+
 ENTRYPOINT ["dotnet", "Uchu.Master/bin/Debug/netcoreapp3.1/Uchu.Master.dll"]

config.xml → config.default.xml

@@ -2,10 +2,10 @@
 <Uchu xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   <Database>
     <Provider>postgres</Provider>
-    <Database>uchu</Database>
+    <Database>$POSTGRES_DB</Database>
     <Host>db</Host>
-    <Username>uchu</Username>
-    <Password>uchu</Password>
+    <Username>$POSTGRES_USER</Username>
+    <Password>$POSTGRES_PASSWORD</Password>
   </Database>
   <ConsoleLogging>
     <Level>Debug</Level>