feat: OpenFeature provider for Go

Makefile

@@ -1,14 +1,18 @@
-.PHONY: build test test-example-1 clean setup-monorepo update-monorepo
+.PHONY: build test test-openfeature test-example-1 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
 
 clean:

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)
@@ -839,6 +840,61 @@ 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
+```
+
+```go
+import (
+    "context"
+
+    featurevisor "github.com/featurevisor/featurevisor-go"
+    featurevisorof "github.com/featurevisor/featurevisor-go/openfeature"
+    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

openfeature/go.mod

@@ -0,0 +1,15 @@
+module github.com/featurevisor/featurevisor-go/openfeature
+
+go 1.25.0
+
+require (
+	github.com/featurevisor/featurevisor-go v1.0.0
+	github.com/open-feature/go-sdk v1.17.2
+)
+
+require (
+	github.com/go-logr/logr v1.4.3 // indirect
+	go.uber.org/mock v0.6.0 // indirect
+)
+
+replace github.com/featurevisor/featurevisor-go => ..

openfeature/go.sum

@@ -0,0 +1,16 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
+github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
+github.com/open-feature/go-sdk v1.17.2 h1:pTdeNks/hgnPrlqdgtFwltnIron1oOxqg4FmLlirJlY=
+github.com/open-feature/go-sdk v1.17.2/go.mod h1:kTMCquVtck18XdSCI6rBoNFEBLvkOy4Tphu2pV8bq34=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+go.uber.org/mock v0.6.0 h1:hyF9dfmbgIX5EfOdasqLsWD6xqpNZlXblLB/Dbnwv3Y=
+go.uber.org/mock v0.6.0/go.mod h1:KiVJ4BqZJaMj4svdfmHM0AUx4NJYO8ZNpPnZn1Z+BBU=
+golang.org/x/text v0.35.0 h1:JOVx6vVDFokkpaq1AEptVzLTpDe9KGpj5tR4/X+ybL8=
+golang.org/x/text v0.35.0/go.mod h1:khi/HExzZJ2pGnjenulevKNX1W67CUy0AsXcNubPGCA=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=