Go SDK reference

Overview

This topic documents how to get started with the Go SDK, and links to reference information on all of the supported features.

Get started

After you complete the Getting Started process, follow these instructions to start using the LaunchDarkly SDK in your Go application.

Install the SDK

First, install the LaunchDarkly SDK as a dependency in your application. How you do this depends on what dependency management system you are using:

• If you are using the standard Go modules system, import the SDK packages in your code and go build will automatically download them. The SDK and its dependencies are modules.
• If you are using dep, import the SDK packages in your code and run dep ensure.
• Otherwise, use the go get command and specify the SDK version, such as go get github.com/launchdarkly/go-server-sdk/v6.

There are several packages that you can import, depending on which features you are using. You usually need the following:

import (
    // go-sdk-common/v3/ldcontext defines LaunchDarkly's model for contexts
    "github.com/launchdarkly/go-sdk-common/v3/ldcontext"
    // go-sdk-common/v3/ldmigration defines LaunchDarkly's model for migration feature flags
    "github.com/launchdarkly/go-sdk-common/v3/ldmigration"
    // go-server-sdk/v7 is the main SDK package - here we are aliasing it to "ld"
    ld "github.com/launchdarkly/go-server-sdk/v7"
    // go-server-sdk/v7/ldcomponents is for advanced configuration options
    "github.com/launchdarkly/go-server-sdk/v7/ldcomponents"
)
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It is good practice to pin your dependencies to a specific version. Refer to the SDK releases page to identify the latest version. When you update your version of go-server-sdk, you should also update go-sdk-common.

Initialize the client

After you install and import the SDK, create a single, shared instance of LDClient. Specify your SDK key here to authorize your application to connect to a particular environment within LaunchDarkly.

This example assumes you've imported the LaunchDarkly SDK package as ld, as shown above.

client, _ := ld.MakeClient("sdk-key-123abc", 5*time.Second)
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The second argument to MakeClient is a timeout parameter. In this example, you are telling the SDK that it can spend up to five seconds attempting to connect to LaunchDarkly services before returning to your application. For more details about what the timeout means and what happens if initialization fails, read MakeClient.

To learn more about the specific configuration options available for this SDK, read Config.

Evaluate a context

Using the LDClient methods, you can check which variation a particular context should receive for a given feature flag. To learn more, read Evaluating flags and Flag evaluation reasons. For more information about how contexts are specified, read Context configuration.

In the v6 example, the context key is the string "context-key-123abc". In the v5 example, the user key is the string "user-key-123abc":

import (
    "github.com/launchdarkly/go-sdk-common/v3/ldcontext"
)
flagKey := "flag-key-123abc"
context := ldcontext.NewBuilder("context-key-123abc").
    Name("Sandy").
    Build()
showFeature, _ := client.BoolVariation(flagKey, context, false)
if showFeature {
    // Application code to show the feature
} else {
    // The code to run if the feature is off
}
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HTTPS Proxy

Go's standard HTTP library provides a built-in HTTPS proxy. If the HTTPS_PROXY environment variable is present, then the SDK will proxy all network requests through the URL provided.

Here is an example:

export HTTPS_PROXY=https://web-proxy.domain.com:8080
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You can also specify a proxy programmatically through the SDK configuration:

var config ld.Config
config.HTTP = ldcomponents.HTTPConfiguration().
    ProxyURL("https://web-proxy.domain.com:8080")
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Shut down the client

Shut down the client when your application terminates. To learn more, read Shutting down.

Supported features

This SDK supports the following features:

• Anonymous contexts and users
• Big segments
• Configuration, including
  • Application metadata configuration
  • Migration configuration
  • Service endpoint configuration
• Context configuration
• Evaluating flags
• Flag evaluation reasons
• Flushing events
• Getting all flags
• Hooks
• Identifying and changing contexts
• Logging configuration
• Migrations
• Monitoring SDK status
• Offline mode
• OpenTelemetry
• Private attributes
• Reading flags from a file
• Relay Proxy configuration
  • Using proxy mode
  • Using daemon mode
• Secure mode
• Sending custom events
• Shutting down
• Storing data
• Subscribing to flag changes
• Test data sources
• Web proxy configuration