mount go cache during docker build

Dockerfile

@@ -1,25 +1,21 @@
-FROM golang:1.14-alpine AS base
+FROM golang:1.14-alpine AS builder
 RUN apk add -U --no-cache \
-        build-base \
-        ca-certificates \
-        git \
-        sqlite \
-        taglib-dev
+    build-base \
+    ca-certificates \
+    git \
+    sqlite \
+    taglib-dev
 WORKDIR /src
 COPY go.mod .
 COPY go.sum .
-ENV GO111MODULE=on
 RUN go mod download
-
-FROM base AS builder
-WORKDIR /src
 COPY . .
 RUN ./_do_build_server && ./_do_build_scanner
 
-FROM alpine
+FROM alpine:3.9
 RUN apk add -U --no-cache \
-	ffmpeg \
-	ca-certificates
+    ffmpeg \
+    ca-certificates
 COPY --from=builder \
     /usr/lib/libgcc_s.so.1 \
     /usr/lib/libstdc++.so.6 \

Dockerfile.dev

@@ -0,0 +1,35 @@
+# syntax=docker/dockerfile:experimental
+
+FROM golang:1.14-alpine AS builder
+RUN apk add -U --no-cache \
+    build-base \
+    ca-certificates \
+    git \
+    sqlite \
+    taglib-dev
+WORKDIR /src
+COPY . .
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    ./_do_build_server && ./_do_build_scanner
+
+FROM alpine:3.9
+RUN apk add -U --no-cache \
+    ffmpeg \
+    ca-certificates
+COPY --from=builder \
+    /usr/lib/libgcc_s.so.1 \
+    /usr/lib/libstdc++.so.6 \
+    /usr/lib/libtag.so.1 \
+    /usr/lib/
+COPY --from=builder \
+    /src/gonic \
+    /src/gonicscan \
+    /bin/
+VOLUME ["/data", "/music", "/cache"]
+EXPOSE 80
+ENV GONIC_DB_PATH /data/gonic.db
+ENV GONIC_LISTEN_ADDR :80
+ENV GONIC_MUSIC_PATH /music
+ENV GONIC_CACHE_PATH /cache
+CMD ["gonic"]