feat: OpenFeature provider for Go

.github/workflows/checks.yml

@@ -3,40 +3,86 @@ name: Checks
 on:
   push:
     branches: ["**"]
+  pull_request:
+
+permissions:
+  contents: read
 
 jobs:
-  ci:
+  sdk:
+    name: SDK (Go ${{ matrix.go }})
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        go: ["1.21.x", "1.25.x"]
 
     steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
-      - name: Set up Go
-        uses: actions/setup-go@v5
+      - uses: actions/setup-go@v6
         with:
-          go-version: "1.22"
+          go-version: ${{ matrix.go }}
+          cache-dependency-path: go.sum
 
-      - name: Install dependencies
-        run: go mod tidy
+      - name: Test SDK
+        run: go test -race ./...
 
-      - name: Build
+      - name: Build CLI
         run: make build
 
-      - name: Test
-        run: make test
+  openfeature:
+    name: OpenFeature provider
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.25.x"
+          cache-dependency-path: |
+            go.sum
+            openfeature/go.sum
+
+      - name: Test provider
+        run: make test-openfeature
+
+      - name: Verify module boundaries
+        run: make verify-packages
+
+  example:
+    name: Featurevisor example-1
+    runs-on: ubuntu-latest
 
-      - uses: actions/setup-node@v4
+    steps:
+      - uses: actions/checkout@v7
         with:
-          node-version-file: ".nvmrc"
+          path: featurevisor-go
 
-      - name: Setup Featurevisor example-1 project
+      - uses: actions/checkout@v7
+        with:
+          repository: featurevisor/featurevisor
+          ref: main
+          path: featurevisor
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.25.x"
+          cache-dependency-path: featurevisor-go/go.sum
+
+      - uses: actions/setup-node@v7
+        with:
+          node-version-file: "featurevisor/.nvmrc"
+          cache: npm
+          cache-dependency-path: featurevisor/package-lock.json
+
+      - name: Build Featurevisor CLI
+        working-directory: featurevisor
         run: |
-          mkdir example-1
-          (cd example-1 && npx @featurevisor/cli@2.x init --example=1)
-          (cd example-1 && npm install)
-          (cd example-1 && npx featurevisor build)
-          (cd example-1 && npx featurevisor test)
-
-      - name: Run Featurevisor project tests against Go SDK
-        run: go run ./cmd/main.go test --projectDirectoryPath=./example-1
+          npm ci
+          npm run build
+
+      - name: Run example-1 through Go SDK
+        working-directory: featurevisor-go
+        run: go run ./cmd/main.go test --projectDirectoryPath=../featurevisor/examples/example-1 --onlyFailures

.github/workflows/release.yml

@@ -0,0 +1,38 @@
+name: Release validation
+
+on:
+  push:
+    tags:
+      - "v*"
+      - "openfeature/v*"
+
+permissions:
+  contents: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.25.x"
+          cache-dependency-path: |
+            go.sum
+            openfeature/go.sum
+
+      - name: Validate tag and modules
+        shell: bash
+        run: |
+          if [[ "$GITHUB_REF_NAME" == openfeature/* ]]; then
+            [[ "$GITHUB_REF_NAME" =~ ^openfeature/v2\.[0-9]+\.[0-9]+(-[0-9A-Za-z.-]+)?$ ]]
+          else
+            [[ "$GITHUB_REF_NAME" =~ ^v2\.[0-9]+\.[0-9]+(-[0-9A-Za-z.-]+)?$ ]]
+          fi
+          make verify-packages
+
+      - name: Test SDK and provider
+        run: make test

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2025 Fahad Heylaal (https://fahad19.com)
+Copyright (c) 2026 Fahad Heylaal (https://fahad19.com)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Makefile

@@ -1,16 +1,25 @@
-.PHONY: build test test-example-1 clean setup-monorepo update-monorepo
+.PHONY: build test test-openfeature test-example-1 verify-packages clean setup-monorepo update-monorepo
 
 build:
 	mkdir -p build
 	go build -o build/featurevisor-go cmd/main.go
 
 test:
 	go test ./...
+	$(MAKE) test-openfeature
+
+test-openfeature:
+	(cd openfeature && GOWORK=off go test ./...)
 
 test-example-1:
-	go test ./...
+	$(MAKE) test
 	go run cmd/main.go test --projectDirectoryPath=../featurevisor/examples/example-1 --onlyFailures
 
+verify-packages:
+	test "$$(go list -m)" = "github.com/featurevisor/featurevisor-go/v2"
+	test "$$(cd openfeature && GOWORK=off go list -m)" = "github.com/featurevisor/featurevisor-go/openfeature/v2"
+	(cd openfeature && GOWORK=off go list -deps ./... >/dev/null)
+
 clean:
 	rm -rf build
 

README.md

@@ -45,6 +45,7 @@ See example application [here](https://github.com/featurevisor/featurevisor-exam
   - [Registering modules](#registering-modules)
 - [Child instance](#child-instance)
 - [Close](#close)
+- [OpenFeature](#openfeature)
 - [CLI usage](#cli-usage)
   - [Test](#test)
   - [Benchmark](#benchmark)
@@ -62,7 +63,7 @@ See example application [here](https://github.com/featurevisor/featurevisor-exam
 In your Go application, install the SDK using Go modules:
 
 ```bash
-go get github.com/featurevisor/featurevisor-go
+go get github.com/featurevisor/featurevisor-go/v2
 ```
 
 ## Public API
@@ -77,6 +78,8 @@ f := featurevisor.CreateFeaturevisor(featurevisor.FeaturevisorOptions{
 
 Most applications only need `CreateFeaturevisor`, the `Featurevisor` instance type, and `FeaturevisorOptions`. Public extension and observability types include `FeaturevisorModule`, `FeaturevisorDiagnostic`, and the datafile model types.
 
+Concurrent evaluations are safe after an instance is configured. Do not call state-changing methods such as `SetDatafile`, `SetContext`, `SetSticky`, `AddModule`, `RemoveModule`, or `Close` concurrently with evaluations or with each other. Apply those changes from a serialized update path. Module, event, and diagnostic callbacks must synchronize mutable state that they capture.
+
 ## Initialization
 
 The SDK can be initialized by passing [datafile](https://featurevisor.com/docs/building-datafiles/) content directly:
@@ -88,7 +91,7 @@ import (
     "io"
     "net/http"
 
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 func main() {
@@ -150,7 +153,7 @@ You can set context at the time of initialization:
 
 ```go
 import (
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 f := featurevisor.CreateFeaturevisor(featurevisor.FeaturevisorOptions{
@@ -335,7 +338,7 @@ Sticky values belong to an SDK or child instance. Evaluation options do not acce
 
 ```go
 import (
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 f := featurevisor.CreateFeaturevisor(featurevisor.FeaturevisorOptions{
@@ -462,7 +465,7 @@ import (
     "io"
     "net/http"
 
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 func updateDatafile(f *featurevisor.Featurevisor, datafileURL string) {
@@ -643,7 +646,7 @@ If `Setup` panics, the module is not registered. Featurevisor removes subscripti
 
 ```go
 import (
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 myCustomModule := &featurevisor.FeaturevisorModule{
@@ -702,7 +705,7 @@ You can register modules at the time of SDK initialization:
 
 ```go
 import (
-    "github.com/featurevisor/featurevisor-go"
+    "github.com/featurevisor/featurevisor-go/v2"
 )
 
 f := featurevisor.CreateFeaturevisor(featurevisor.FeaturevisorOptions{
@@ -721,6 +724,8 @@ removeModule()
 
 ## Child instance
 
+A child snapshots the parent keys that exist when it is spawned. Child values win for those keys. Parent keys introduced later are still inherited. Calling `Close()` removes both child-owned listeners and subscriptions delegated to the parent.
+
 When dealing with purely client-side applications, it is understandable that there is only one user involved, like in browser or mobile applications.
 
 But when using Featurevisor SDK in server-side applications, where a single server instance can handle multiple user requests simultaneously, it is important to isolate the context for each request.
@@ -746,8 +751,11 @@ Similar to parent SDK, child instances also support several additional methods:
 
 - `SetContext`
 - `SetSticky`
+- `EvaluateFlag`
 - `IsEnabled`
+- `EvaluateVariation`
 - `GetVariation`
+- `EvaluateVariable`
 - `GetVariable`
 - `GetVariableBoolean`
 - `GetVariableString`
@@ -798,12 +806,12 @@ go run cmd/main.go test \
 If you want to validate parity locally against the JavaScript SDK runner, you can use the bundled example project:
 
 ```bash
-cd /Users/fahad/Projects/featurevisor/featurevisor/examples/example-1
+cd ../featurevisor/examples/example-1
 npx featurevisor test
 
 # from this Go SDK repository root:
 go run cmd/main.go test \
-  --projectDirectoryPath="/Users/fahad/Projects/featurevisor/featurevisor/examples/example-1" \
+  --projectDirectoryPath="../featurevisor/examples/example-1" \
   --onlyFailures
 
 # or:
@@ -839,6 +847,61 @@ go run cmd/main.go assess-distribution \
     --n=1000
 ```
 
+## OpenFeature
+
+The OpenFeature provider is a separate Go module, so applications that do not use OpenFeature do not receive its dependencies:
+
+```bash
+go get github.com/featurevisor/featurevisor-go/openfeature/v2
+```
+
+```go
+import (
+    "context"
+
+    featurevisor "github.com/featurevisor/featurevisor-go/v2"
+    featurevisorof "github.com/featurevisor/featurevisor-go/openfeature/v2"
+    of "github.com/open-feature/go-sdk/openfeature"
+)
+
+provider := featurevisorof.NewProvider(featurevisorof.Options{
+    FeaturevisorOptions: featurevisor.FeaturevisorOptions{
+        Datafile: datafileContent,
+    },
+})
+
+if err := of.SetProviderAndWait(provider); err != nil {
+    panic(err)
+}
+
+client := of.NewClient("")
+enabled, err := client.BooleanValue(
+    context.Background(),
+    "checkout",
+    false,
+    of.NewEvaluationContext("user-123", map[string]any{"country": "nl"}),
+)
+```
+
+Use `checkout` for a flag, `checkout:variation` for its variation, and `checkout:title` for its `title` variable. Boolean variables use the boolean resolver. Arrays, objects, and JSON variables use the object resolver.
+
+OpenFeature's targeting key maps to `userId` by default. `TargetingKeyField`, `KeySeparator`, and `VariationKey` can customize the mapping. The provider's separate module follows the Go version requirement of the official OpenFeature Go SDK.
+
+You can also reuse an existing Featurevisor instance:
+
+```go
+fv := featurevisor.CreateFeaturevisor(featurevisor.FeaturevisorOptions{
+    Datafile: datafileContent,
+})
+provider := featurevisorof.NewProvider(featurevisorof.Options{
+    Featurevisor: fv,
+})
+```
+
+The caller owns an instance passed this way. Provider shutdown does not close it. Call `fv.Close()` when every consumer is finished with it. When the provider creates the instance from `FeaturevisorOptions`, the provider owns and closes it. If both fields are supplied, `Featurevisor` takes precedence over `FeaturevisorOptions`.
+
+See the [OpenFeature provider guide](https://featurevisor.com/docs/sdks/openfeature/) for resolution reasons, errors, metadata, tracking, lifecycle, and providers for other languages.
+
 <!-- FEATUREVISOR_DOCS_END -->
 
 ## Development of this package
@@ -859,8 +922,10 @@ go test ./...
 
 ### Releasing
 
-- Manually create a new release on [GitHub](https://github.com/featurevisor/featurevisor-go/releases)
-- Tag it with a prefix of `v`, like `v1.0.0`
+- Tag the core SDK as `v2.x.y`.
+- Tag the provider module separately as `openfeature/v2.x.y`.
+- Run `make verify-packages` before creating either release.
+- Create the matching releases on [GitHub](https://github.com/featurevisor/featurevisor-go/releases).
 
 ## License
 

api_compatibility_test.go

@@ -104,6 +104,21 @@ func TestAPICompatibilityWithStringFeatureKey(t *testing.T) {
 	if childVariable == nil {
 		t.Error("Expected child variable to be returned")
 	}
+
+	flagEvaluation := child.EvaluateFlag("test-feature")
+	if flagEvaluation.Enabled == nil || !*flagEvaluation.Enabled {
+		t.Fatalf("expected child flag evaluation to be enabled, got %#v", flagEvaluation)
+	}
+
+	variationEvaluation := child.EvaluateVariation("test-feature")
+	if variationEvaluation.VariationValue == nil || string(*variationEvaluation.VariationValue) != *childVariation {
+		t.Fatalf("expected child variation evaluation to match getter, got %#v", variationEvaluation)
+	}
+
+	variableEvaluation := child.EvaluateVariable("test-feature", "color")
+	if variableEvaluation.VariableValue != "blue" {
+		t.Fatalf("expected child variable evaluation value blue, got %#v", variableEvaluation)
+	}
 }
 
 func TestAPICompatibilityWithNonExistentFeature(t *testing.T) {