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Bootstrap Go

It is hard to write bootstrap tool to quickly create Go service. So I write this guide instead. This is a quick checklist for me every damn time I need to write a Go service from scratch. Also, this is my personal opinion, so feel free to comment.

Structure

main.go
internal
| business_1
| | http
| | | handler.go
| | | service.go
| | | repository.go
| | | models.go
| | grpc
| | | handler.go
| | | service.go
| | | repository.go
| | | models.go
| | service.go
| | repository.go
| | models.go
| business_2
| | grpc
| | | handler.go
| | | service.go
| | | repository.go
| | | models.go

All business codes are inside internal. Each business has a different directory (business_1, business_2).

Inside each business, there are 2 handlers: http, grpc:

http is for public APIs (Android, iOS,... are clients).
grpc is for internal APIs (other services are clients).

Inside each handler, there are usually 3 layers: handler, service, repository:

handler interacts directly with gRPC or REST using specific codes (cookies,...)
service is where we write business/logic codes, and only business/logic codes is written here.
repository is where we write codes which interacts with database/cache like MySQL, Redis, ...

handler must exist inside grpc, http. But service, repository, models can exist directly inside business if both grpc, http has same business/logic.

Do not repeat!

If we have too many services, some of the logic will be overlapped.

For example, service A and service B both need to make POST call API to service C. 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. 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.

Another bad practice is adapter service. No need to write a new service if what we need is just common pkg libs.

Taste on style guide

Use functional options, but don't overuse it!

For simple struct with 1 or 2 fields, no need to use functional options.

Example:

func main() {
	s := NewS(WithA(1), WithB("b"))
	fmt.Printf("%+v\n", s)
}

type S struct {
	fieldA int
	fieldB string
}

type OptionS func(s *S)

func WithA(a int) OptionS {
	return func(s *S) {
		s.fieldA = a
	}
}

func WithB(b string) OptionS {
	return func(s *S) {
		s.fieldB = b
	}
}

func NewS(opts ...OptionS) *S {
	s := &S{}
	for _, opt := range opts {
		opt(s)
	}
	return s
}

In above example, I construct s with WithA and WithB option. No need to pass direct field inside s.

External libs

Don't use cli libs (spf13/cobra, urfave/cli) just for Go service

What is the point to pass many params (--abc, --xyz) when what we only need is start service?

In my case, service starts with only config, and config should be read from file or environment like The Twelve Factors guide.

Don't use grpc-ecosystem/grpc-gateway

Just don't.

Use protocolbuffers/protobuf-go, grpc/grpc-go for gRPC.

Write 1 for both gRPC, REST sounds good, but in the end, it is not worth it.

Don't use uber/prototool, use bufbuild/buf

prototool is deprecated, and buf can generate, lint, format as good as prototool.

Use gin-gonic/gin for REST.

Don't use gin.Context when pass context from handler layer to service layer, use gin.Context.Request.Context() instead.

If you want log, just use uber-go/zap

It is fast!

Don't overuse func (*Logger) With. Because if log line is too long, there is a possibility that we can lost it.
Use MarshalLogObject when we need to hide some field of object when log (field has long or sensitive value)
Don't use Panic. Use Fatal for errors when start service to check dependencies. If you really need panic level, use DPanic.
Use contextID or traceID in every log lines for easily debug.

Don't overuse ORM libs, no need to handle another layer above SQL.

Each ORM libs has each different syntax. To learn and use those libs correctly is time consuming. So just stick to plain SQL. It is easier to debug when something is wrong.

But database/sql has its own limit. For example, it is hard to get primary key after insert/update. So may be you want to use ORM for those cases.

If you want test, just use stretchr/testify.

It is easy to write a suite test, thanks to testify. Also, for mocking, there are many options out there. Pick 1 then sleep peacefully.

Replace `go fmt`, `goimports` with mvdan/gofumpt.

gofumpt provides more rules when format Go codes.

Use golangci/golangci-lint.

No need to say more. Lint or get the f out!

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