Pass hadolint

Dockerfile-backend

@@ -1,19 +1,19 @@
-FROM golang:alpine as gobuild
+FROM golang:1-alpine as gobuild
 
 RUN apk add --no-cache git
 
 WORKDIR /go/src/srs.epita.fr/fic-server/
 
-ADD go.mod go.sum ./
-ADD settings settings/
-ADD libfic ./libfic/
-ADD backend ./backend/
+COPY go.mod go.sum ./
+COPY settings settings/
+COPY libfic ./libfic/
+COPY backend ./backend/
 
-RUN go get -d -v ./backend
-RUN go build -v -o backend/backend ./backend
+RUN go get -d -v ./backend && \
+    go build -v -o backend/backend ./backend
 
 
-FROM alpine
+FROM alpine:3.14
 
 WORKDIR /srv