How to build, run and test go2 files locally

#go #docker #generics

I worked recently on an in-memory key, value cache with Go and I used interface{} for the key, value types since I didn't want to restrict their usage to a specific type. Now with Generics in go, I refactored this package such that you could explicitly set the types of the key and value when instantiating the cache. I found it difficult to run go2 code locally hence this blogpost.

Dependencies

Docker

Approach

Luckily, there's a docker image with the go2go tool already installed (levonet/golang:go2go). The idea here is to build/run/test the go2 code inside this docker container.

Build

Write your go2 code in a file ending in .go2 e.g cache.go2. From the directory where the file is located, run the command below to build the it

docker run --rm -v "$PWD":/go/src/myapp -w /go/src/myapp levonet/golang:go2go go tool go2go build

Run

Similarly, you can run your code using the command

docker run --rm -v "$PWD":/go/src/myapp -w /go/src/myapp levonet/golang:go2go go tool go2go run

Test

You could also test using the command

docker run --rm -v "$PWD":/go/src/myapp -w /go/src/myapp levonet/golang:go2go go tool go2go test

Creavats

The go2go command doesn't support go modules. I had to work around this by creating a custom docker file with steps to download my dependencies manually.
I can't get test coverage using the go2go test tool. It can do the tests but since it translates the go code inside the same file as the _test.go file. I couldn't get test coverage for files in this directory.

Workarounds

I solved the go.mod problem by creating a custom Dockerfile which downloads my dependencies and adds them to the go2go build path

FROM levonet/golang:go2go

## "apt-get update" updates package list
## "apt-get install git -y" installs 'git' the "-y" flag is there to answer yes to all prompts
RUN apt-get update && apt-get install git -y

# This command clones the dependencies in my GOPATH
RUN git clone https://github.com/dgrijalva/lfu-go /go/src/github.com/dgrijalva/lfu-go && \
    git clone https://github.com/arschles/assert /go/src/github.com/arschles/assert

# This command copies all my files in the directory /go/src/myapp in the container
COPY ./ /go/src/myapp

## This changes the working directory
WORKDIR /go/src/myapp

Build the docker image using the command below the -t cache is to tag the image as cache

docker build . -t cache

You can now build/run/test the .go2 code using the commands below

# Test
docker run --rm lfucache go tool go2go test

# Build
docker run --rm lfucache go tool go2go build

# Run
docker run --rm lfucache go tool go2go run

This can also be done with a CI/CD tool like travis. I have the following travis file the lfucache package

services:
  - docker

before_install:
  # This builds the docker file containing the tests
  - docker build . -t lfucache

script:
  # This tests the go2 files
  - docker run --rm lfucache go tool go2go test

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