Go

Install the latest version

Github | pkg

go get github.com/ReforgeHQ/sdk-go@latest

Initialize Client

Add reforge "github.com/ReforgeHQ/sdk-go" to your imports.

Then, initialize the client with your SDK key:

sdk, err := reforge.NewSdk(reforge.WithSdkKey(sdkKey))

Typical Usage

We recommend using the SDK client as a singleton in your application.

import reforge "github.com/ReforgeHQ/sdk-go"

var reforgeSdk reforge.ClientInterface

func init() {
    // Note: WithSdkKey is not needed if REFORGE_BACKEND_SDK_KEY env var is set
    sdk, err := reforge.NewSdk()
    if err != nil {
        panic(err)
    }
    reforgeSdk = sdk
}

Feature Flags

For boolean flags, you can use the FeatureIsOn function:

enabled, ok := sdk.FeatureIsOn("my.feature.name", reforge.ContextSet{})

Flags that don't exist yet are considered off, so you can happily add FeatureIsOn checks to your code before the flag is created.

Feature flags don't have to return just true or false.

You can get other data types using Get* functions:

value, ok, err := sdk.GetStringValue("my.string.feature.name", reforge.ContextSet{})
value, ok, err := sdk.GetJSONValue("my.json.feature.name", reforge.ContextSet{})

Context

Feature flags become more powerful when we give the flag evaluation rules more information to work with. We do this by providing context of the current user (and/or team, request, etc.)

Global Context

When initializing the client, you can set a global context that will be used for all evaluations.

globalContext := reforge.NewContextSet().
    WithNamedContextValues("host", map[string]interface{}{
        "name": os.Getenv("HOSTNAME"),
        "region":   os.Getenv("REGION"),
        "cpu":      runtime.NumCPU(),
    })


sdk, err := reforge.NewSdk(
    reforge.WithSdkKey(sdkKey),
    reforge.WithGlobalContext(globalContext),
)

Global context is the least specific context and will be overridden by more specific context passed in at the time of evaluation.

Bound Context

To make the best use of Reforge in a web setting, we recommend setting context per-request. Setting this context for the life-cycle of the request means the Reforge logger can be aware of your user/etc. for feature flags and targeted log levels and you won't have to explicitly pass context into your .FeatureIsOn and .Get* calls.

requestContext := reforge.NewContextSet().
    WithNamedContextValues("user", map[string]interface{}{
        "name":  currentUser.GetName(),
        "email": currentUser.GetEmail(),
    })

boundSdk := sdk.WithContext(requestContext)
enabled, ok := boundSdk.FeatureIsOn("my.feature.name", reforge.ContextSet{})

Just-in-time Context

You can also pass context when evaluating individual flags or config values.

enabled, ok := boundSdk.FeatureIsOn("my.feature.name", reforge.NewContextSet().
    WithNamedContextValues("team", map[string]interface{}{
        "name":  currentTeam.GetName(),
        "email": currentTeam.GetEmail(),
    }))

Dynamic Config

Config values are available via the Get* functions:

value, ok, err := sdk.GetJSONValue("slack.bot.config", reforge.ContextSet{})

value, ok, err := sdk.GetStringValue("some.string.config", reforge.ContextSet{})

value, ok, err := sdk.GetFloatValue("some.float.config", reforge.ContextSet{})

Default Values for Configs

Here we ask for the value of a config named max-jobs-per-second, and we specify 10 as a default value if no value is available.

value, wasFound := sdk.GetIntValueWithDefault("max-jobs-per-second", 10, reforge.ContextSet{})

If max-jobs-per-second is available, wasFound will be true and value will be the value of the config. If max-jobs-per-second is not available, wasFound will be false and value will be 10.

Dynamic Log Levels

Reforge provides real-time dynamic log level control for popular Go logging libraries. When you change a log level in Reforge, it takes effect immediately in your application via SSE without any polling or restarts.

Standard Library (slog)

The SDK includes built-in support for Go's standard library log/slog package with no additional dependencies:

import (
    "log/slog"
    "os"
    reforge "github.com/ReforgeHQ/sdk-go"
)

sdk, _ := reforge.NewSdk(reforge.WithSdkKey("your-key"))

// Create a Reforge handler that wraps your base handler
baseHandler := slog.NewJSONHandler(os.Stdout, nil)
handler := reforge.NewReforgeHandler(sdk, baseHandler, "com.example.myapp")
logger := slog.New(handler)

// Log levels are controlled dynamically by Reforge
logger.Debug("Debug message")
logger.Info("Info message")
logger.Error("Error message")

Alternatively, use ReforgeLeveler with HandlerOptions:

leveler := reforge.NewReforgeLeveler(sdk, "com.example.myapp")
handler := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
    Level: leveler,
})
logger := slog.New(handler)

Third-Party Logger Integrations

Reforge provides optional integrations for popular third-party logging libraries. These are available as separate modules to keep the main SDK dependency-free:

Zap

go get github.com/ReforgeHQ/sdk-go/integrations/zap

import (
    reforge "github.com/ReforgeHQ/sdk-go"
    reforgezap "github.com/ReforgeHQ/sdk-go/integrations/zap"
    "go.uber.org/zap"
)

sdk, _ := reforge.NewSdk(reforge.WithSdkKey("your-key"))

// Option 1: Using IncreaseLevel
dynamicLevel := reforgezap.NewReforgeZapLevel(sdk, "com.example.myapp")
logger, _ := zap.NewProduction(zap.IncreaseLevel(dynamicLevel))

// Option 2: Using custom core
encoder := zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig())
core := reforgezap.NewReforgeZapCore(
    zapcore.NewCore(encoder, zapcore.AddSync(os.Stdout), zapcore.DebugLevel),
    sdk,
    "com.example.myapp",
)
logger := zap.New(core)

View zap integration docs on GitHub

Zerolog

go get github.com/ReforgeHQ/sdk-go/integrations/zerolog

import (
    reforge "github.com/ReforgeHQ/sdk-go"
    reforgezerolog "github.com/ReforgeHQ/sdk-go/integrations/zerolog"
    "github.com/rs/zerolog"
)

sdk, _ := reforge.NewSdk(reforge.WithSdkKey("your-key"))
hook := reforgezerolog.NewReforgeZerologHook(sdk, "com.example.myapp")
logger := zerolog.New(os.Stdout).Hook(hook).With().Timestamp().Logger()

View zerolog integration docs on GitHub

Charmbracelet Log

go get github.com/ReforgeHQ/sdk-go/integrations/charmbracelet

import (
    reforge "github.com/ReforgeHQ/sdk-go"
    charmbracelet "github.com/ReforgeHQ/sdk-go/integrations/charmbracelet"
    "github.com/charmbracelet/log"
)

sdk, _ := reforge.NewSdk(reforge.WithSdkKey("your-key"))
baseLogger := log.New(os.Stdout)
logger := charmbracelet.NewReforgeCharmLogger(sdk, baseLogger, "com.example.myapp")

View charmbracelet integration docs on GitHub

Configuration

Create a LOG_LEVEL_V2 config in your Reforge dashboard with key log-levels:

# Default to INFO for all loggers
default: INFO

# Set specific packages to DEBUG
rules:
  - criteria:
      reforge-sdk-logging.logger-path:
        starts-with: "com.example.services"
    value: DEBUG

  # Only log errors in noisy third-party library
  - criteria:
      reforge-sdk-logging.logger-path:
        starts-with: "github.com/somelib"
    value: ERROR

You can customize the config key name using the WithLoggerKey option. This is useful if you have multiple applications sharing the same Reforge project and want to isolate log level configuration per application:

sdk, _ := reforge.NewSdk(
    reforge.WithSdkKey("your-key"),
    reforge.WithLoggerKey("myapp.log.levels"),
)

The SDK automatically includes lang: "go" in the evaluation context, which you can use in your rules to create Go-specific log level configurations:

# Different log levels for Go vs other languages
rules:
  - criteria:
      reforge-sdk-logging.lang: go
      reforge-sdk-logging.logger-path:
        starts-with: "com.example"
    value: DEBUG

  - criteria:
      reforge-sdk-logging.lang: java
      reforge-sdk-logging.logger-path:
        starts-with: "com.example"
    value: INFO

Targeted Log Levels

You can use rules and segmentation to change your log levels based on the current user/request/device context. This allows you to increase log verbosity for specific users, environments, or conditions without affecting your entire application.

The log level evaluation has access to all context that is available during evaluation, not just the reforge-sdk-logging context. This means you can create rules combining:

• SDK logging context (reforge-sdk-logging.*) - Logger name and language
• Global context - Application name, environment, availability zone, etc.
• Dynamic context - User, team, device, request information from bound or just-in-time context

For example, you can create rules like:

# Enable DEBUG logs only for specific application in staging
rules:
  - criteria:
      application.key: "myapp"
      application.environment: "staging"
      reforge-sdk-logging.logger-path:
        starts-with: "com.example"
    value: DEBUG

  # Enable DEBUG logs for a specific user across all applications
  - criteria:
      user.email: "developer@example.com"
    value: DEBUG

  # Lower verbosity in production
  - criteria:
      application.environment: "production"
    value: WARN

This allows you to increase log verbosity for specific users, specific applications, particular environments, or any combination of conditions without affecting your entire system.

How It Works

All logger integrations check Reforge configuration on every log call for real-time updates. When you change a log level in Reforge, it takes effect immediately via SSE without any polling or manual refresh. Different components can have different log levels using different logger names.

Telemetry

By default, Reforge uploads telemetry that enables a number of useful features. You can alter or disable this behavior using the following options:

Name	Description	Default
collectEvaluationSummaries	Send counts of config/flag evaluation results back to Reforge to view in web app	true
contextTelemetryMode	Upload either context "shapes" (the names and data types your app uses in Reforge contexts) or periodically send full example contexts	PERIODIC_EXAMPLE

If you want to change any of these options, you can pass options when initializing the Reforge SDK:

sdk, err := reforge.NewSdk(
    reforge.WithSdkKey(sdkKey),
    reforge.WithCollectEvaluationSummaries(true),
    reforge.WithContextTelemetryMode(reforge.ContextTelemetryMode.PeriodicExample),
)

Available context telemetry modes:

• reforge.ContextTelemetryMode.None - Don't upload any context information
• reforge.ContextTelemetryMode.Shapes - Upload only context shapes (names and data types)
• reforge.ContextTelemetryMode.PeriodicExample - Periodically send full example contexts (default)

To disable all telemetry at once:

sdk, err := reforge.NewSdk(
    reforge.WithAllTelemetryDisabled(),
)

Offline and Testing Modes

Offline Sources (Datafiles)

For offline development, testing, or air-gapped environments, you can use datafiles instead of connecting to the Reforge API. See Testing with DataFiles for more information on generating and using datafiles.

When using offline sources, you must provide the WithProjectEnvID to identify which environment's configuration you're using:

sdk, err := reforge.NewSdk(
    reforge.WithProjectEnvID(123456789), // Your project environment ID
    reforge.WithOfflineSources([]string{
        "datafile:///path/to/your/datafile.json",
    }),
)

Important notes:

• WithOfflineSources excludes the default API and SSE sources - the SDK will only use the sources you specify
• Telemetry is automatically disabled when using offline sources
• You can find your project environment ID in the Reforge UI or from your datafile metadata

In-Memory Configs (Testing)

If you need to test multiple scenarios that depend on a single config or feature key, you can set up an SDK with in-memory configs:

configs := map[string]interface{}{
	"string.key": "value",
	"int.key":    int64(42),
	"bool.key":   true,
	"float.key":  3.14,
	"slice.key":  []string{"a", "b", "c"},
	"json.key": map[string]interface{}{
		"nested": "value",
	},
}

client, err := reforge.NewSdk(reforge.WithConfigs(configs))

Reference

Options

client, err := reforge.NewSdk(
    reforge.WithSdkKey(os.Getenv("REFORGE_SDK_KEY")), // or use REFORGE_BACKEND_SDK_KEY env var
    reforge.WithGlobalContext(globalContext),
    reforge.WithCollectEvaluationSummaries(true),
    reforge.WithContextTelemetryMode(reforge.ContextTelemetryMode.PeriodicExample),
)

Option Definitions

Name	Description	Default
WithSdkKey	Your Reforge SDK key (not needed if REFORGE_BACKEND_SDK_KEY env var is set)	from env var
WithProjectEnvID	Project environment ID (required when using WithOfflineSources)	nil
WithOfflineSources	Use offline data sources (datafiles) instead of API/SSE. Automatically disables telemetry. Requires WithProjectEnvID	nil
WithGlobalContext	Set a static context to be used as the base layer in all configuration evaluation	empty
WithCollectEvaluationSummaries	Send counts of config/flag evaluation results back to Reforge to view in web app	true
WithContextTelemetryMode	Upload either context "shapes" (the names and data types your app uses in Reforge contexts) or periodically send full example contexts	PERIODIC_EXAMPLE
WithAllTelemetryDisabled	Disable all telemetry (evaluation summaries and context telemetry)	n/a
WithConfigs	Provide in-memory configs for testing	nil
WithOnInitializationFailure	Choose to crash or continue with local data only if unable to fetch config data from Reforge at startup	RAISE (crash)
WithInitializationTimeoutSeconds	Timeout for initial config fetch	10
WithLoggerKey	Config key for LOG_LEVEL_V2 configuration	log-levels