Debugging a Go Application Inside a Docker Container

Table of Contents

So we need: straight arms and basin with docker preinstalled:

cat Dockerfile

FROM golang:1.13

WORKDIR /go/src/app
COPY . .

RUN go get -u github.com/go-delve/delve/cmd/dlv

CMD ["app"]

and then run: docker build -t my-golang-app .

This is just one of the options, sometimes you need to start dlv instead of bash and so on.

$ docker run -it --rm my-golang-app bash

$ root@03c1977b1063:/go/src/app# dlv main.go
Error: unknown command "main.go" for "dlv"
Run 'dlv --help' for usage.
root@03c1977b1063:/go/src/app# dlv debug main.go
could not launch process: fork/exec /go/src/app/__debug_bin: operation not permitted

OOps…

So let’s add the parameters:

$ docker run -it --rm --security-opt="apparmor=unconfined" --cap-add=SYS_PTRACE my-golang-app bash

voila 🎉

$ root@7dc3a7e8b3fc:/go/src/app# dlv debug main.go
Type 'help' for list of commands.
(dlv)

P.S. same trick can be used with docker-compose or multi-stage builds. If you are interested in how to debug multi-stage builds on Go, please put “+” in the comments or throw a tomato 🍅.