Go SDK reference

Overview

This reference guide documents all of the methods available in the Go SDK, and explains how these methods work. LaunchDarkly's SDKs are open source. The source is available in its GitHub repository and its generated API reference.

You can also use this SDK to clone and run a sample application.

Getting started

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

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 gopkg.in/launchdarkly/go-server-sdk.v5.

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

import (
    // go-sdk-common.v2/lduser defines LaunchDarkly's model for user properties
    "gopkg.in/launchdarkly/go-sdk-common.v2/lduser"
    // go-server-sdk.v5 is the main SDK package - here we are aliasing it to "ld"
    ld "gopkg.in/launchdarkly/go-server-sdk.v5"
    // go-server-sdk.v5/ldcomponents is for advanced configuration options
    "gopkg.in/launchdarkly/go-server-sdk.v5/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.

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("YOUR_SDK_KEY", 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.

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

In this example, the user key is an email address:

import (
    "gopkg.in/launchdarkly/go-sdk-common.v2/lduser"
)
flagKey := "some-flag-key"
user := lduser.NewUser("some-user-key")
showFeature, _ := client.BoolVariation(flagKey, user, 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:

import (
    ld "gopkg.in/launchdarkly/go-server-sdk.v5"
    "gopkg.in/launchdarkly/go-server-sdk.v5/ldcomponents"
)
var config ld.Config
config.HTTP = ldcomponents.HTTPConfiguration().
    ProxyURL("https://web-proxy.domain.com:8080")
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Shutting down

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

Supported features

This SDK supports the following features:

• Aliasing users
• Big Segments
• Configuration
• Evaluating flags
• Flag evaluation reasons
• Flushing events
• Getting all flags
• Identifying and changing users
• Logging configuration
• Monitoring SDK status
• Offline mode
• Reading flags from a file
• Secure mode
• Sending custom events
• Shutting down
• Storing data
• Subscribing to flag changes
• Test data sources
• User configuration