<!doctype html><metacharset=utf-8><metaname=viewportcontent="width=device-width,initial-scale=1"><linkrel=preconnecthref=https://fonts.googleapis.com><linkrel=preconnecthref=https://fonts.gstatic.comcrossorigin><linkhref="https://fonts.googleapis.com/css2?family=Recursive:wght,CASL,MONO@300..800,0..1,0..1&display=swap"rel=stylesheet><linkhref=https://haunt98.github.io/iosevka_webfont/iosevka-term-ss08/iosevka-term-ss08.cssrel=stylesheet><linkrel=stylesheethref=styles.css><ahref=index>Index</a><h1>Bootstrap Go</h1><p>It is hard to write bootstrap tool to quickly create Go service.<br>So I write this guide instead.<br>This is a quick checklist for me every damn time I need to write a Go service from scratch.<br>Also, this is my personal opinion, so feel free to comment.<h2>Structure</h2><pre><codeclass=language-txt>main.go
</code></pre><p>All business codes are inside <code>internal</code>.<br>Each business has a different directory <code>business</code>.<p>Inside each business, there are 2 handlers: <code>http</code>, <code>grpc</code>:<ul><li><code>http</code> is for public APIs (Android, iOS, ... are clients).<li><code>grpc</code> is for internal APIs (other services are clients).<li><code>consumer</code> is for consuming messages from queue (Kafka, RabbitMQ, ...).</ul><p>For each handler, there are usually 3 layers: <code>handler</code>, <code>service</code>, <code>repository</code>:<ul><li><code>handler</code> interacts directly with gRPC, REST or consumer using specific codes (cookies, ...) In case gRPC, there are frameworks outside handle for us so we can write business/logic codes here too. But remember, gRPC only.<li><code>service</code> is where we write business/logic codes, and only business/logic codes is written here.<li><code>repository</code> is where we write codes which interacts with database/cache like MySQL, Redis, ...<li><code>models</code> is where we put all request, response, data models.</ul><p>Location:<ul><li><code>handler</code> must exist inside <code>grpc</code>, <code>http</code>, <code>consumer</code>.<li><code>service</code>, <code>models</code> can exist directly inside of <code>business</code> if both <code>grpc</code>, <code>http</code>, <code>consumer</code> has same business/logic.<li><code>repository</code> should be placed directly inside of <code>business</code>.</ul><h2>Do not repeat!</h2><p>If we have too many services, some of the logic will be overlapped.<p>For example, service A and service B both need to make POST call API to service C.<br>If service A and service B both have libs to call service C to do that API, we need to move the libs to some common pkg libs.<br>So in the future, service D which needs to call C will not need to copy libs to handle service C api but only need to import from common pkg libs.<p>Another bad practice is adapter service.<br>No need to write a new service if what we need is just common pkg libs.<h2>Taste on style guide</h2><h3>Stop using global var</h3><p>If I see someone using global var, I swear I will shoot them twice in the face.<p>Why?<ul><li>Can not write unit test.<li>Is not thread safe.</ul><h3>Use functional options, but don't overuse it!</h3><p>For simple struct with 1 or 2 fields, no need to use functional options.<p><ahref=https://go.dev/play/p/0XnOLiHuoz3>Example</a>:<pre><codeclass=language-go>func main() {
</code></pre><p>In above example, I construct <code>s</code> with <code>WithA</code> and <code>WithB</code> option.<br>No need to pass direct field inside <code>s</code>.<h3>Use <ahref=https://pkg.go.dev/golang.org/x/sync/errgroup>errgroup</a> as much as possible</h3><p>If business logic involves calling too many APIs, but they are not depend on each other.<br>We can fire them parallel :)<p>Personally, I prefer <code>errgroup</code> to <code>WaitGroup</code> (<ahref=https://pkg.go.dev/sync#WaitGroup)>https://pkg.go.dev/sync#WaitGroup)</a>.<br>Because I always need deal with error.<p>Example:<pre><codeclass=language-go>eg, egCtx := errgroup.WithContext(ctx)
</code></pre><h3>Use <ahref=https://pkg.go.dev/golang.org/x/sync/semaphore>semaphore</a> when need to implement WorkerPool</h3><p>Please don't use external libs for WorkerPool, I don't want to deal with dependency hell.<h2>External libs</h2><h3>No need <code>vendor</code></h3><p>Only need if you need something from <code>vendor</code>, to generate mock or something else.<h3>Use <code>build.go</code> to include build tools in go.mod</h3><p>To easily control version of build tools.<p>For example <code>build.go</code>:<pre><codeclass=language-go>//go:build tools
</code></pre><p>We always get the version of build tools in <code>go.mod</code> each time we install it.<br>Future contributors will not cry anymore.<h3>Don't use cli libs (<ahref=https://github.com/spf13/cobra>spf13/cobra</a>, <ahref=https://github.com/urfave/cli>urfave/cli</a>) just for Go service</h3><p>What is the point to pass many params (<code>do-it</code>, <code>--abc</code>, <code>--xyz</code>) when what we only need is start service?<p>In my case, service starts with only config, and config should be read from file or environment like <ahref=https://12factor.net/>The Twelve Factors</a> guide.<h3>Don't use <ahref=https://github.com/grpc-ecosystem/grpc-gateway>grpc-ecosystem/grpc-gateway</a></h3><p>Just don't.<p>Use <ahref=https://github.com/protocolbuffers/protobuf-go>protocolbuffers/protobuf-go</a>, <ahref=https://github.com/grpc/grpc-go>grpc/grpc-go</a> for gRPC.<p>Write 1 for both gRPC, REST sounds good, but in the end, it is not worth it.<h3>Don't use <ahref=https://github.com/uber/prototool>uber/prototool</a>, use <ahref=https://github.com/bufbuild/buf>bufbuild/buf</a></h3><p>prototool is deprecated, and buf can generate, lint, format as good as prototool.<h3>Use <ahref=https://github.com/gin-gonic/gin>gin-gonic/gin</a> for REST.</h3><p>Don't use <code>gin.Context</code> when pass context from handler layer to service layer, use <code>gin.Context.Request.Context()</code> instead.<h3>If you want log, just use <ahref=https://github.com/uber-go/zap>uber-go/zap</a></h3><p>It is fast!<ul><li>Don't overuse <code>func (*Logger) With</code>. Because if log line is too long, there is a possibility that we can lost it.<li>Use <code>MarshalLogObject</code> when we need to hide some field of object when log (field is long or has sensitive value)<li>Don't use <code>Panic</code>. Use <code>Fatal</code> for errors when start service to check dependencies. If you really need panic level, use <code>DPanic</code>.<li>If doubt, use <code>zap.Any</code>.<li>Use <code>contextID</code> or <code>traceID</code> in every log lines for easily debug.</ul><h3>To read config, use <ahref=https://github.com/spf13/viper>spf13/viper</a></h3><p>Only init config in main or cmd layer.<br>Do not use <code>viper.Get...</code> in business layer or inside business layer.<p>Why?<ul><li>Hard to mock and test<li>Put all config in single place for easily tracking</ul><p>Also, be careful if config value is empty.<br>You should decide to continue or stop the service if there is no config.<h3>Don't overuse ORM libs, no need to handle another layer above SQL.</h3><p>Each ORM libs has each different syntax.<br>To learn and use those libs correctly is time consuming.<br>So just stick to plain SQL.<br>It is easier to debug when something is wrong.<p>But <code>database/sql</code> has its own limit.<br>For example, it is hard to get primary key after insert/update.<br>So may be you want to use ORM for those cases.<br>I hear that <ahref=https://github.com/go-gorm/gorm>go-gorm/gorm</a>, <ahref=https://github.com/ent/ent>ent/ent</a> is good.<h3>If you want test, just use <ahref=https://github.com/stretchr/testify>stretchr/testify</a>.</h3><p>It is easy to write a suite test, thanks to testify.<br>Also, for mocking, there are many options out there.<br>Pick 1 then sleep peacefully.<h3>If need to mock, choose <ahref=https://github.com/matryer/moq>matryer/moq</a> or <ahref=https://github.com/golang/mock>golang/mock</a></h3><p>The first is easy to use but not powerful as the later.<br>If you want to make sure mock func is called with correct times, use the later.<p>Example with <code>matryer/moq</code>:<pre><codeclass=language-go>// Only gen mock if source code file is newer than mock file
</code></pre><h3>Use <ahref=https://pkg.go.dev/golang.org/x/tools/cmd/stringer>stringer</a> if you want your type enum can be print as string</h3><pre><codeclass=language-go>type Drink int
</code></pre><h3>Don't waste your time rewrite rate limiter if your use case is simple, use <ahref=https://pkg.go.dev/golang.org/x/time/rate>rate</a> or <ahref=https://github.com/go-redis/redis_rate>go-redis/redis_rate</a></h3><p>rate if you want rate limiter locally in your single instance of service.<br>redis_rate if you want rate limiter distributed across all your instances of service.<h3>Replace <code>go fmt</code>, <code>goimports</code> with <ahref=https://github.com/mvdan/gofumpt>mvdan/gofumpt</a>.</h3><p><code>gofumpt</code> provides more rules when format Go codes.<h3>Use <ahref=https://github.com/golangci/golangci-lint>golangci/golangci-lint</a>.</h3><p>No need to say more.<br>Lint or get the f out!<p>If you get <code>fieldalignment</code> error, use <ahref=https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/fieldalignment>fieldalignment</a> to fix them.<pre><codeclass=language-sh># Install
</code></pre><h2>Thanks</h2><ul><li><ahref=https://github.com/uber-go/guide/blob/master/style.md>Uber Go Style Guide</a><li><ahref=https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis>Functional options for friendly APIs</a><li><ahref=https://google.github.io/styleguide/go/index>Google Go Style</a></ul><ahref=mailto:hauvipapro+posts@gmail.com>Feel free to ask me via email</a>
