Building and Deploying Go Applications
There is a SLE BCI that can be used with the Go programming language. There are a couple different recommended methods to work with the Go SLE BCI.
Don’t Ship The Compiler
Go is a compiled language producing a binary as the end result. That means the compiler does not need to be shipped as part of the images that are distributed. Instead, it is recommended that the Go image is used as the builder image only.
By not shipping the Go compiler with your application, the attack surface area of the containerized application is reduced and the overall image size is much smaller.
Using Go As A Builder Image
There are two ways to work with Go images. First, you can encapsulate
your application in a scratch
container image, which is essentially an empty image. This approach
will not function if your Go application depends on libc or any other
library, as they will not be available.
A second method is to use a slim base container image with just the minimal packages needed. The General Purpose SLE BCI images offer four different options here, depending on your exact requirements.
Building from scratch
The following Dockerfile illustrates building an application using
the SLE BCI Go image to compile the binary and then copying it into a
new image based on scratch. The example uses a hello world
as the program name, which can be substituted for the real application
name.
# Build the Go Binary using the SLE BCI Go 1.19 images
FROM registry.suse.com/bci/golang:1.19 as build
WORKDIR /app
COPY go.mod ./
COPY go.sum ./
RUN go mod download
COPY *.go ./
# Make sure to build the application with CGO disabled. This will force Go to
# use some Go implementations of code rather than those normally supplied by the
# host operating system. You need this for scratch images as those supporting
# libraries are not available.
RUN CGO_ENABLED=0 go build -o /hello-world
# Create image to bundle app
FROM scratch
COPY --from=build /hello-world /hello-world
CMD ["/hello-world"]Additional settings like exposing network ports or running as a
non-root user can be specified in the last step below the FROM
scratch line.
Building from SLE BCI
Applications that require external libraries or CA certificates cannot
be deployed into a scratch image. A General Purpose SLE BCI should
be used instead. The above Dockerfile has to be slightly adjusted
in this case:
# Build the Go Binary using the SLE BCI Go 1.19 images
FROM registry.suse.com/bci/golang:1.19 as build
WORKDIR /app
COPY go.mod ./
COPY go.sum ./
RUN go mod download
COPY *.go ./
RUN go build -o /hello-world
# Create image to bundle app
FROM registry.suse.com/bci/bci-micro:15.4
# Install dependencies (if required) here
COPY --from=build /hello-world /usr/local/bin/hello-world
CMD ["/usr/local/bin/hello-world"]The above example uses the SLE BCI micro image as the deployment image for the resulting application. This is just one of the options, other options can be found in the section about the General Purpose SLE BCI.