golang bump to v6; adds initialization instructions (#498)

* golang bump to v6; adds initialization instructions

* pre and post instructions

* Update docs/sdks/server-sdks/go.md

Co-authored-by: Oleksii Shmalko <[email protected]>

---------

Co-authored-by: Oleksii Shmalko <[email protected]>

Author: leoromanovsky

docs/sdks/server-sdks/go.md

@@ -14,14 +14,14 @@ In your `go.mod`, add the SDK package as a dependency:
 
 ```
 require (
-	github.com/Eppo-exp/golang-sdk/v5
+	github.com/Eppo-exp/golang-sdk/v6
 )
 ```
 
 Or you can install the SDK from the command line with:
 
 ```
-go get github.com/Eppo-exp/golang-sdk/v5
+go get github.com/Eppo-exp/golang-sdk/v6
 ```
 
 ## 2. Initialize the SDK
@@ -31,7 +31,7 @@ Initialize the SDK with a SDK key, which can be generated in the Eppo interface.
 ```go
 
 import (
-  "github.com/Eppo-exp/golang-sdk/v5/eppoclient"
+  "github.com/Eppo-exp/golang-sdk/v6/eppoclient"
 )
 
 var eppoClient = &eppoclient.EppoClient{}
@@ -40,11 +40,41 @@ func main() {
   eppoClient, err = eppoclient.InitClient(eppoclient.Config{
     SdkKey: "<your_sdk_key>",
   })
+
+  select {
+    case <-client.Initialized():
+    case <-time.After(2 * time.Second):
+      log.Warn("Timed out waiting for Eppo SDK to initialize")
+  }
 }
 ```
 
 After initialization, the SDK begins polling Eppo's API at regular intervals to retrieve the most recent experiment configurations such as variation values and traffic allocation. The SDK stores these configurations in memory so that assignments thereafter are effectively instant. For more information, see the [architecture overview](/sdks/architecture/overview) page.
 
+### Waiting for initialization
+
+Depending on your server application's lifecycle, you may need to wait for the SDK to initialize before making assignments
+
+Starting with the `6.1.0` tag, the `Initialized` channel is provided to facilitate this and can optionally be used with a timeout to allow you application to continue.
+
+Before this tag, the SDK was initialized asynchronously and assignments could be made immediately but will not be guaranteed to have the most recent experiment configurations, returning the `DEFAULT-VALUE` if the SDK was not initialized in time. If this is not desired in your application, a suggested approach on older versions is to introduce a brief delay after startup to allow the SDK to initialize before making assignments.
+
+```go
+import (
+  "time"
+)
+
+func main() {
+  eppoClient, err = eppoclient.InitClient(eppoclient.Config{
+    SdkKey: "<your_sdk_key>",
+  })
+
+  time.Sleep(2 * time.Second)
+
+  variation, err := eppoClient.GetStringAssignment("<FLAG-KEY>", "<SUBJECT-KEY>", <TARGETING-ATTRIBUTES>, <DEFAULT-VALUE>);
+}
+```
+
 ### Define an assignment logger (experiment assignment only)
 
 If you are using the Eppo SDK for experiment assignment (i.e randomization), pass in a callback logging function to the `InitClient` function on SDK initialization. The SDK invokes the callback to capture assignment data whenever a variation is assigned.
@@ -63,7 +93,7 @@ Example implementation:
 
 ```go
 import (
-  "github.com/Eppo-exp/golang-sdk/v5/eppoclient"
+  "github.com/Eppo-exp/golang-sdk/v6/eppoclient"
   "gopkg.in/segmentio/analytics-go.v3"
 )
 
@@ -86,7 +116,7 @@ func main() {
   client := analytics.New("YOUR_WRITE_KEY")
   defer client.Close()
 
-  eppoClient = eppoclient.InitClient(eppoclient.Config{
+  eppoClient, _ = eppoclient.InitClient(eppoclient.Config{
     SdkKey:           "<your_sdk_key>",
     AssignmentLogger: &ExampleAssignmentLogger{
       client: client,
@@ -120,7 +150,7 @@ Assigning users to flags or experiments with a single `GetStringAssignment` func
 
 ```go
 import (
-	"github.com/Eppo-exp/golang-sdk/v5/eppoclient"
+	"github.com/Eppo-exp/golang-sdk/v6/eppoclient"
 )
 
 var eppoClient = &eppoclient.EppoClient{} // in global scope
@@ -144,6 +174,7 @@ GetNumericAssignment(...) (float64, error)
 GetIntegerAssignment(...) (int, error)
 GetStringAssignment(...) (string, error)
 GetJSONAssignment(...) (interface{}, error)
+GetJSONBytesAssignment(...) ([]byte, error)
 ```
 
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