--- title: Go SDK description: Set up the Flagship OpenFeature provider to evaluate Flagship feature flags from Go server applications. image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/flagship/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # Go SDK The Go SDK provides an OpenFeature-compatible server provider for Go applications. It evaluates flags over HTTP and does not support the Cloudflare Workers binding. ## Installation Install with `go get`: Terminal window ``` go get github.com/cloudflare/flagship/sdks/go ``` ## Setup Configure the provider with your Flagship app ID, Cloudflare account ID, and an API token with Flagship Evaluate permission. ``` package main import ( "context" "log" flagship "github.com/cloudflare/flagship/sdks/go" "github.com/open-feature/go-sdk/openfeature") func main() { ctx := context.Background() provider, err := flagship.NewProvider(flagship.Options{ AppID: "", AccountID: "", AuthToken: "", }) if err != nil { log.Fatal(err) } if err := openfeature.SetProviderAndWait(provider); err != nil { log.Fatal(err) } defer openfeature.Shutdown() client := openfeature.NewDefaultClient() evalCtx := openfeature.NewEvaluationContext("user-42", map[string]any{ "plan": "enterprise", }) enabled, err := client.BooleanValue(ctx, "new-checkout", false, evalCtx) if err != nil { log.Fatal(err) } log.Println("new-checkout:", enabled)} ``` ## Flag types The Go SDK supports all OpenFeature server-side flag types. ``` enabled, _ := client.BooleanValue(ctx, "new-checkout", false, evalCtx)variant, _ := client.StringValue(ctx, "homepage-hero", "control", evalCtx)rate, _ := client.FloatValue(ctx, "sample-rate", 0.1, evalCtx)limit, _ := client.IntValue(ctx, "upload-limit", 10, evalCtx)config, _ := client.ObjectValue(ctx, "ui-config", map[string]any{"theme": "light"}, evalCtx) ``` Use the `*ValueDetails` methods when you need reason, variant, metadata, or error codes. ## Response caching The provider can cache evaluations to avoid a network round-trip for repeated flag/context pairs. Caching is off by default and enabled by setting `CacheTTL`: ``` provider, err := flagship.NewProvider(flagship.Options{ AppID: "", AccountID: "", AuthToken: "", CacheTTL: 30 * time.Second, // values may be up to this stale CacheMaxSize: 1000, // LRU-evicted beyond this many entries}) ``` Each cache entry is keyed by flag key, flag type, and the full evaluation context, so distinct contexts never share a cached value. Cache hits resolve with `reason == openfeature.CachedReason`. Disabled flags, errors, and type mismatches are never cached. Because freshness is TTL-based, a flag change in Flagship takes effect after the entry expires. The cache is per-provider instance, guarded by a mutex for concurrent use, and cleared on `Shutdown`. ## Configuration options | Option | Description | | -------------- | -------------------------------------------------------------------------------------------------------- | | AppID | Flagship app ID. | | AccountID | Required with AppID. | | BaseURL | Base URL override. Defaults to https://api.cloudflare.com. | | AuthToken | Adds Authorization: Bearer to each request. | | Headers | Static headers. Explicit Authorization overrides AuthToken. | | HeadersFactory | Dynamic per-request headers. Values override Headers and AuthToken. | | HTTPClient | Custom HTTP client. | | Timeout | Per-attempt timeout. Defaults to 5 seconds. | | Retries | Retry attempts on transient errors. Defaults to 1 and is capped at 10. | | DisableRetries | Disables retries when set to true. | | RetryDelay | Delay between retries. Defaults to 1 second and is capped at 30 seconds. | | CacheTTL | Enables in-memory response caching when greater than 0\. Cached values may be up to this duration stale. | | CacheMaxSize | Maximum number of cached entries. LRU-evicted beyond this limit. Defaults to 1000 when CacheTTL is set. | | Logging | Enables debug and error logging. Off by default. | | Logger | Optional slog\-compatible logger. Uses the default slog logger when unset. | | Hooks | Provider-level OpenFeature hooks. | ## Evaluation context Context attributes are sent as URL query parameters. Supported values are strings, numeric types, booleans, and `time.Time`. `nil` values are skipped. Maps, slices, structs, and other complex values return `INVALID_CONTEXT` through OpenFeature and do not trigger an HTTP request. ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/flagship/sdk/go/#page","headline":"Go SDK ยท Cloudflare Flagship docs","description":"Set up the Flagship OpenFeature provider to evaluate Flagship feature flags from Go server applications.","url":"https://developers.cloudflare.com/flagship/sdk/go/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","dateModified":"2026-06-30","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/flagship/","name":"Flagship"}},{"@type":"ListItem","position":3,"item":{"@id":"/flagship/sdk/","name":"OpenFeature SDK"}},{"@type":"ListItem","position":4,"item":{"@id":"/flagship/sdk/go/","name":"Go SDK"}}]} ```