reusing docker stages

Dockerfile

@@ -1,24 +1,10 @@
-# building the go program
-FROM golang:1.15.6-alpine AS builder
-RUN apk add --no-cache git
-ENV GO111MODULE=on \
-    CGO_ENABLED=0 \
-    GOOS=linux \
-    GOARCH=amd64
-
-WORKDIR /src
-COPY go.mod go.sum ./
-RUN go mod download
-COPY main.go ./
-COPY core ./core/
-RUN go build -o gogodiscordo
-
 # downloading mbrola voice
 FROM alpine as alpine_voices
 WORKDIR /tmp
 RUN wget --no-check-certificate https://github.com/numediart/MBROLA-voices/archive/master.zip \
     && unzip master.zip && rm master.zip
 
+
 # final image
 FROM ubuntu:focal as ubuntu1
 
@@ -35,7 +21,28 @@ RUN set -ex;\
 
 RUN mkdir -p /usr/share/mbrola/
 
-COPY --from=builder /src/gogodiscordo /app/
+
+# setting up builder
+FROM golang:1.15.6-alpine AS builder
+RUN apk add --no-cache git
+ENV GO111MODULE=on \
+    CGO_ENABLED=0 \
+    GOOS=linux \
+    GOARCH=amd64
+
+WORKDIR /src
+
+# compiling the go project
+FROM builder as builder2
+COPY go.mod go.sum ./
+RUN go mod download
+COPY main.go ./
+COPY core ./core/
+RUN go build -o gogodiscordo
+
+
+FROM ubuntu1 as ubuntu2
+COPY --from=builder2 /src/gogodiscordo /app/
 COPY config.yaml /app/
 COPY --from=alpine_voices /tmp/MBROLA-voices-master/data/fr* /usr/share/mbrola/