FeatBit Go Server SDK

When to Use This Skill

Use for server-side Go applications — HTTP servers, background workers, CLI tools — that need real-time feature flag evaluation.

Why server-side SDK: maintains one persistent WebSocket connection, synchronizes all flag data locally in under 100 ms, then evaluates every flag locally in under 10 ms per call on average. Do not use for frontend JavaScript or mobile applications — those require a client-side SDK.

Source

https://github.com/featbit/featbit-go-sdk

Setup Workflow

Copy and track progress:

Step 1: Install the module
Step 2: Create the client with secret and URLs
Step 3: Build the user and evaluate the first feature flag
Step 4: If initialization fails, validate configuration and retry
Step 5: Read advanced README sections only when needed

Step 1: Install the module

Run:

go get github.com/featbit/featbit-go-sdk

Step 2: Create the client

Use this minimal setup:

client, err := featbit.NewFBClient(envSecret, streamingUrl, eventUrl)
if err != nil {
  return err
}
defer client.Close()

Step 3: Evaluate the first feature flag

Use the official pattern:

user, _ := interfaces.NewUserBuilder("<unique-user-key>").UserName("Jane").Build()
_, detail, _ := client.BoolVariation("flag-key", user, false)
fmt.Printf("flag %s returns %s, reason: %s\n", detail.KeyName, detail.Variation, detail.Reason)

Step 4: Validate the integration

If client.IsInitialized() is false or evaluation returns the fallback unexpectedly, verify envSecret, streamingUrl, and eventUrl, then retry.

Feature Flag Evaluation

After the client is initialized, evaluate a feature flag with a user and a fallback value:

user, _ := interfaces.NewUserBuilder("<unique-user-key>").UserName("Jane").Build()
value, detail, _ := client.BoolVariation("flag-key", user, false)
fmt.Println(value, detail.Reason)

Use the first return value when only the flag result is needed. Use detail when the evaluation reason is also needed — detail.Reason explains why the value was returned, detail.KeyName and detail.Variation identify the matched variation.

Also available for non-boolean flags: Variation (string), IntVariation, DoubleVariation, JsonVariation.

User Custom Properties

Add custom properties to FBUser when targeting rules depend on user attributes beyond key and userName:

user, _ := interfaces.NewUserBuilder("a-unique-key-of-user").
    UserName("bob").
    Custom("age", "15").
    Custom("country", "FR").
    Build()

Use Custom(key, value) for any attribute that must be referenced in feature flag targeting rules.