Multi-stage Dockerfiles for Golang

DOCKERFILE

# Using "go proxy"
# TODO: how do I separate the build from download
#       using goproxy?

########################################
## FIRST STAGE: build the application ##
########################################

FROM golang:1.14-alpine AS builder

# Install certificates
RUN apk --no-cache add \
    ca-certificates \
    && update-ca-certificates

# Set the Current Working Directory inside the container
WORKDIR /go/src/github.com/CESARBR/knot-babeltower

# Copy the source code from the current directory to $WORKDIR (inside the container)
COPY . .

# Build the app for linux target (cross compile disabled)
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
    GO111MODULE=on GOPROXY=https://proxy.golang.org \
    go build -a -installsuffix cgo -o app cmd/main.go

###########################################
## SECOND STAGE: create production image ##
###########################################

# FROM alpine:3.11
FROM scratch

WORKDIR /root/

# Copy the configuration files from the build stage
COPY --from=builder /go/src/github.com/CESARBR/knot-babeltower/internal/ ./internal

# Copy the binary file from the build stage
COPY --from=builder /go/src/github.com/CESARBR/knot-babeltower/app app

# Copy SSL CA certificates
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

ENTRYPOINT ["./app"]

Dockerfile

# Using "go mod download"

########################################
## FIRST STAGE: build the application ##
########################################

FROM golang:1.14-alpine AS builder

# Install build dependencies
RUN apk --no-cache add --virtual .build-deps \
    make \
    git

# Install certificates
RUN apk --no-cache add \
    ca-certificates \
    && update-ca-certificates

# Set the Current Working Directory inside the container
WORKDIR /go/src/github.com/CESARBR/knot-babeltower

# Populate the module cache based on the go.{mod,sum} files
COPY go.mod .
COPY go.sum .

# Download dependancies (cached if the go.{mod,sum} files aren't changed)
RUN go mod download
RUN go mod verify

# Copy the source code from the current directory to $WORKDIR (inside the container)
COPY . .

# Build the app for linux target (cross compile disabled)
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
    go build -a -installsuffix cgo -o app cmd/main.go

# # Remove build dependencies
RUN apk del .build-deps

###########################################
## SECOND STAGE: create production image ##
###########################################

# FROM alpine:3.11
FROM scratch

WORKDIR /root/

# Copy the configuration files from the build stage
COPY --from=builder /go/src/github.com/CESARBR/knot-babeltower/internal/ ./internal

# Copy the binary file from the build stage
COPY --from=builder /go/src/github.com/CESARBR/knot-babeltower/app app

# Copy SSL CA certificates
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

ENTRYPOINT ["./app"]