Add RELEASE instructions and Docker files. (#247)

# docker build . --rm --build-arg version=2.0.4 --build-arg commit=master -t heroiclabs/nakama:2.0.4

## Copyright 2018 The Nakama Authors

##

## Licensed under the Apache License, Version 2.0 (the "License");

## you may not use this file except in compliance with the License.

## You may obtain a copy of the License at

##

## http:##www.apache.org/licenses/LICENSE-2.0

##

## Unless required by applicable law or agreed to in writing, software

## distributed under the License is distributed on an "AS IS" BASIS,

## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

## See the License for the specific language governing permissions and

## limitations under the License.

# docker build "$PWD" --build-arg commit=d79ccd1 --build-arg version=v2.1.0 -t heroiclabs/nakama:2.1.0

FROM golang:1.11.1-alpine3.7 as builder

ARG commit

ARG version

RUN apk --no-cache add ca-certificates gcc musl-dev git

ENV GOOS linux

ENV GOARCH amd64

ENV CGO_ENABLED 1

WORKDIR /go/src/github.com/heroiclabs/

RUN git config --global advice.detachedHead false && \

  git clone -q -n https://github.com/heroiclabs/nakama

RUN apk --no-cache add ca-certificates gcc musl-dev git && \

    git config --global advice.detachedHead false && \

    git clone --quiet --no-checkout https://github.com/heroiclabs/nakama /go/src/github.com/heroiclabs/nakama

WORKDIR /go/src/github.com/heroiclabs/nakama

RUN git checkout -q "$commit" && \

  GOOS=linux GOARCH=amd64 go build && \

  mkdir -p /go/build && \

  mv nakama /go/build

RUN git checkout --quiet "$commit" && \

    go build -o /go/build/nakama -gcflags "-trimpath $PWD" -asmflags "-trimpath $PWD" -ldflags "-s -w -X main.version=$version -X main.commitID=$commit"

FROM alpine:3.7

HEALTHCHECK --interval=5m --timeout=3s \

  CMD curl -f http://localhost:7350/ || exit 1

Release Instructions

===

These instructions guide the release process for new official Nakama server builds.

## Steps

To build releases for a variety of platforms we use the excellent [xgo](https://github.com/karalabe/xgo) project. You will need Docker engine installed. These steps should be followed from the project root folder.

These steps are one off to install the required build utilities.

1. Install the xgo Docker image.

   ```

   docker pull karalabe/xgo-latest

   ```

2. Install the command line helper tool. Ensure "$GOPATH/bin" is on your system path to access the executable.

   ```

   env GO111MODULE=off go get -u github.com/karalabe/xgo

   ```

These steps are run for each new release.

1. Update the CHANGELOG.

2. Add the CHANGELOG file and tag a commit.

   __Note__: In source control good semver suggests a "v" prefix on a version. It helps group release tags.

   ```

   git add CHANGELOG

   git commit -m "Nakama 2.1.0 release."

   git tag -a v2.1.0 -m "v2.1.0"

   git push origin v2.1.0 master

   ```

3. Execute the cross-compiled build helper.

   ```

   xgo --targets=darwin/amd64,linux/amd64,linux/arm64,windows/amd64 --ldflags "-s -w -X main.version=2.1.0 -X main.commitID=$(git rev-parse --short HEAD 2>/dev/null)" --branch v2.1.0 github.com/heroiclabs/nakama

   ```

   This will build binaries for all target platforms supported officially by Heroic Labs.

4. Package up each release as a compressed bundle.

   ```

   tar -czf "nakama-<os>-<arch>" nakama README.md LICENSE CHANGELOG.md

   ```

5. Create a new draft release on GitHub and publish it with the compressed bundles.

## Build Nakama Image

With the release generated we can create the official container image.

1. Build the container image.

   ```

   cd build

   docker build "$PWD" --file ./Dockerfile --build-arg commit="$(git rev-parse --short HEAD 2>/dev/null)" --build-arg version=v2.1.0 -t heroiclabs/nakama:2.1.0

   ```

2. Push the image to the container registry.

   ```

   docker push heroiclabs/nakama:2.1.0

   ```

## Build Plugin Builder Image

With the official release image generated we can create a container image to help with Go runtime development.

1. Build the container image.

   ```

   cd build/pluginbuilder

   docker build "$PWD" --file ./Dockerfile --build-arg commit="$(git rev-parse --short HEAD 2>/dev/null)" --build-arg version=v2.1.0 -t heroiclabs/nakama-pluginbuilder:2.1.0

   ```

2. Push the image to the container registry.

   ```

   docker push heroiclabs/nakama-pluginbuilder:2.1.0

   ```

# docker build . --file ./build/plugin.Dockerfile --build-arg src=sample_go_module

FROM golang:1.11.1-alpine3.7 as builder

ARG src

WORKDIR /go/src/$src

COPY $src /go/src/$src

RUN apk --no-cache add ca-certificates gcc musl-dev git && \

  go get -u github.com/heroiclabs/nakama && \

  GOOS=linux go build -buildmode=plugin . && \

  mkdir -p /go/build && \

  mv "/go/src/$src/$src.so" /go/build/

## Copyright 2018 The Nakama Authors

##

## Licensed under the Apache License, Version 2.0 (the "License");

## you may not use this file except in compliance with the License.

## You may obtain a copy of the License at

##

## http:##www.apache.org/licenses/LICENSE-2.0

##

## Unless required by applicable law or agreed to in writing, software

## distributed under the License is distributed on an "AS IS" BASIS,

## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

## See the License for the specific language governing permissions and

## limitations under the License.

# docker build "$PWD" --file ./Dockerfile.pluginbuilder --build-arg commit=d79ccd1 --build-arg version=v2.1.0 -t heroiclabs/nakama-pluginbuilder:2.1.0

FROM golang:1.11.1-alpine3.7 as builder

MAINTAINER Heroic Labs <support@heroiclabs.com>

ARG commit

ARG version

LABEL version=$version

LABEL variant=nakama-pluginbuilder

LABEL description="A support container to build Go code for Nakama server's runtime."

ENV GOOS linux

ENV GOARCH amd64

ENV CGO_ENABLED 1

RUN apk --no-cache add ca-certificates gcc musl-dev git && \

    git config --global advice.detachedHead false && \

    git clone --quiet --no-checkout https://github.com/heroiclabs/nakama.git /go/src/github.com/heroiclabs/nakama && \

    git checkout --quiet "$commit"

WORKDIR /go/src/tempbuild/

ENTRYPOINT ["go"]