Kevlars

A golang backend development kits to accelerate building services.

Background

Having to write over and over again something like logger, db connection, caching, audit log, rest client, grpc client, telemetry, config/secret, healthcheck, feature flag, and so on. I find it waste a lot of time, while it should be re-usable everywhere in multiple service. There-fore come to mind to build a development kits to help me reach that goal. During those development process in private, I find it that this might help anyone whom has the same goal as mine. Thus, I decide to make this project open source. To anyone using this library and have feedback or would like to contribute, please don't hesitate to do so.

Usage

Since on of the purpose of this development kit to accelerate building backend service, below we can see how easy and fast we can scaffold new RESTful API.

scaffold.
    NewApp(scaffold.WithScope("restful_api")).
    WithDatabases().
    RunRestApiUseEcho(func(app *scaffold.Application, e *echo.Echo) {
        // do something such as routing and needed process
        // all resources that instantiate above (e.g. WithDatabase) are available under `app`
        // for example: 
        // if we want to get config value:
        // app.Config().GetString("key")
        // if we want to use database connection:
        // app.DefaultDB().Exec(ctx, q, args...)
})

Another sample when we need to run service as GRPC Server, it would simply be done by following sample:

scaffold.
    NewApp(scaffold.WithScope("restful_api")).
    WithDatabases().
    RunGrpcServer(run func(app *Application, rpcServer *grpc.Server)) {
        // do something such as register proto and needed process
        // all resources that instantiate above (e.g. WithDatabase) are available under `app`
        // for example: 
        // if we want to get config value:
        // app.Config().GetString("key")
        // if we want to use database connection:
        // app.DefaultDB().Exec(ctx, q, args...)
})

For more samples, can refer to directory examples in this repository.

Package Structure and Usage

Audit

This package is used for audit log.

Note: currently only support postgres and mysql

Usage as follows:

dbm := db.New(
	db.DriverPostgreSQL, 
	"host=localhost port=5432 user=db_user password=b4Zd3x6aLRM6mKs2S3 dbname=db_name sslmode=disable", 
	db.WithMaxOpenConnection(30), 
)
al := audit.New(dbm).MustInit()
err := al.Add(context.Background(), audit.Record{
	Action: "do_something",
	CreatedByName: "system",
	BeforeChanged: map[string]interface{}{
		"name": "kevlars",
    },
	AfterChanged: map[string]interface{}{
		"name": "shield",
	}
})
fmt.Println(err)

In Memory

This package is used for In Memory data.

Currently, supported valkey and redis as provider. Will consider add another provider when deemed necessary.

To utilize this package, simply:

ctx := context.Background()
// instantiate with must connect to ensure connection is established else panic
c := inmemory.NewRedis(address).MustConnect(ctx)

// get value user hash
uh := c.GetString(ctx, "user_hash")
fmt.Println(uh)

// delete user hash
err := c.Del(ctx, "user_hash")
fmt.Println(err)

Captcha

This package is used to generate captcha image and validate user input.

Note: currently only support generating base64 encoded image.

To use this package, simply import it and use it like below:

cb64 := captcha.NewB64(captcha.B64WithType(captcha.B64TypeDigit)).MustInit()
// generate base 64 image
// capId => is the captcha id use to validate
// capImg => base 64 encoded image
capId, _, capImg := cb64.Generate()

// to verify user input:
// userInput => should be the variable contains the value of user input
// capId => use the generated id above
isValid := cb64.Verify(capId, userInput, true)
fmt.Println(isValid)

DB

This package is used to connect to database provider

Database supported: PostgreSQL, MySQL and SQL Server

Meanwhile, for SQL Server, it's not fully tested yet -- use at your own risk

Usage:

dbm := db.New(
	db.DriverPostgreSQL, 
	"host=localhost port=5432 user=db_user password=b4Zd3x6aLRM6mKs2S3 dbname=db_name sslmode=disable", 
	db.WithMaxOpenConnection(30), 
)
rows, err := dbm.Query(context.Background(), "SELECT * FROM users")
if err != nil {
	return
}
// ... continue your implementation here

FFlag

This package is used to manage feature flag. Use this on any block of code that you want to be able to turn on/off. Sample usage:

dbm := db.New(
    db.DriverPostgreSQL,
    "host=localhost port=5432 user=db_user password=b4Zd3x6aLRM6mKs2S3 dbname=db_name sslmode=disable",
    db.WithMaxOpenConnection(30),
)
ff := fflag.New(fflag.WithDB(dbm)).MustInit()
ctx := context.Background()
ff.Add(ctx, fflag.Record{
	Feature:"feature_name", 
	Enabled: true, 
	LastChangedBy:"who_is_me",
})
ff.ExecWhenEnabled(ctx, "feature_name", func() {
    // this will be executed when feature_name are enabled	
})

Messaging

This package is used to send messaging to selected provider.

Currently only support sending message to telegram. Will add other provider as things progress.

To use this package, simply import it and use it like below:

tgSender := messaging.NewTelegramSender(
        messaging.TelegramWithTarget(app.Config().GetString("messaging.telegram.default_target")),
        messaging.TelegramWithToken(app.Config().GetString("messaging.telegram.token")),
        messaging.TelegramWithSanitizer(messaging.StandardSanitizer()), 
    ).MustInit()
err := tgSender.SendMessage(`hello!`)
fmt.Println(err)