Use multi stage build

Dockerfile

@@ -1,16 +1,29 @@
+FROM golang AS builder
+
+WORKDIR /app
+
+COPY ./src /app/src
+COPY ./go.mod /app
+COPY ./go.sum /app
+
+RUN go build -o /app/main /app/src/main.go 
+RUN go build -o /app/cmd /app/src/cmd.go 
+
 ARG JAVA_VERSION=16
-FROM openjdk:${JAVA_VERSION}
+FROM openjdk:16
 
 ENV MIN_MEM=512M
 ENV MAX_MEM=1G
 ENV STOP="stop"
 ENV JAR=server.jar
 
-COPY ./bin/main /main
-COPY ./bin/cmd /usr/local/bin/cmd
+COPY --from=builder /app/main /main
+COPY --from=builder /app/cmd /usr/local/bin/cmd
 
 EXPOSE 25565
 
 VOLUME [ "/server" ]
 
+WORKDIR /server
+
 ENTRYPOINT [ "/main" ]

build.sh

@@ -1,6 +1,2 @@
 #!/bin/sh
-
-mkdir -p bin && \
-go build -o bin/main src/main.go && \
-go build -o bin/cmd src/cmd.go && \
 sudo docker build -t magmise/minecraft:latest .