Google App Engine Flex Container Deployment Issues - go

Question

I am trying to deploy my Go 1.14 microservices application on to Google's Flexible environment. I read that there are issues with finding GOROOT, and how it is unable to obtain the correct dependencies.
I wanted to use the flexible environment because I needed to do port forwarding. Since my domain name was used to run the actual application, I wanted port 8081 to run my microservices.
I followed the instruction from this link:
https://blog.cubieserver.de/2019/go-modules-with-app-engine-flexible/
I tried option 3.
This is my gitlab-ci.yaml configurations file.
# .gitlab-ci.yaml
stages:
- build
- deploy
build_server:
stage: build
image: golang:1.14
script:
- go mod vendor
- go install farmcycle.us/user/farmcycle
artifacts:
paths:
- vendor/
deploy_app_engine:
stage: deploy
image: google/cloud-sdk:270.0.0
script:
- echo $SERVICE_ACCOUNT > /tmp/$CI_PIPELINE_ID.json
- gcloud auth activate-service-account --key-file /tmp/$CI_PIPELINE_ID.json
- gcloud --quiet --project $PROJECT_ID app deploy app.yaml
after_script:
- rm /tmp/$CI_PIPELINE_ID.json
This my app.yaml configuration file
runtime: go
env: flex
network:
forwarded_ports:
- 8081/tcp
When I deployed this using the Git CI pipeline. Build stage passes, but the Deploy stage failed.
Running with gitlab-runner 13.4.1 (e95f89a0)
on docker-auto-scale 72989761
Preparing the "docker+machine" executor
Preparing environment
00:03
Getting source from Git repository
00:04
Downloading artifacts
00:02
Executing "step_script" stage of the job script
00:03
$ echo $SERVICE_ACCOUNT > /tmp/$CI_PIPELINE_ID.json
$ gcloud auth activate-service-account --key-file /tmp/$CI_PIPELINE_ID.json
Activated service account credentials for: [farmcycle-hk1996#appspot.gserviceaccount.com]
$ gcloud --quiet --project $PROJECT_ID app deploy app.yaml
ERROR: (gcloud.app.deploy) Staging command [/usr/lib/google-cloud-sdk/platform/google_appengine/go-app-stager /builds/JLiu1272/farmcycle-backend/app.yaml /builds/JLiu1272/farmcycle-backend /tmp/tmprH6xQd/tmpSIeACq] failed with return code [1].
------------------------------------ STDOUT ------------------------------------
------------------------------------ STDERR ------------------------------------
2020/10/10 20:48:27 staging for go1.11
2020/10/10 20:48:27 Staging Flex app: failed analyzing /builds/JLiu1272/farmcycle-backend: cannot find package "farmcycle.us/user/farmcycle/api" in any of:
($GOROOT not set)
/root/go/src/farmcycle.us/user/farmcycle/api (from $GOPATH)
GOPATH: /root/go
--------------------------------------------------------------------------------
Running after_script
00:01
Running after script...
$ rm /tmp/$CI_PIPELINE_ID.json
Cleaning up file based variables
00:01
ERROR: Job failed: exit code 1
This was the error. Honestly I am not really sure what this error is and how to fix it.

Answer 1

Surprisingly, even using the latest Go runtime, runtime: go1.15, go modules appear to not be used. See golang-docker.
However, Flex builds your app into a container regardless of runtime and so, in this case, it may be better to use a custom runtime and build your own Dockerfile?
runtime: custom
env: flex
Then you get to use e.g. Go 1.15 and go modules (without vendoring) and whatever else you'd like. For a simple main.go that uses modules e.g.:
FROM golang:1.15 as build
ARG PROJECT="flex"
WORKDIR /${PROJECT}
COPY go.mod .
RUN go mod download
COPY main.go .
RUN GOOS=linux \
go build -a -installsuffix cgo \
-o /bin/server \
.
FROM gcr.io/distroless/base-debian10
COPY --from=build /bin/server /
USER 999
ENV PORT=8080
EXPOSE ${PORT}
ENTRYPOINT ["/server"]
This ought to be possible with Google's recently announced support for buildpacks but I've not tried it.