[MM-16620] Properly handle analytics client life cycle

Properly handle analytics client life cycle

This change improves the life cycle management of the analytics
client. It does so in two primary ways:
 - Move the client from being a shared pointer to belonging to the
   Server struct.
 - Expose the client.Close() method for proper shutdown of the
   client.

app/server.go

@@ -20,6 +20,7 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/pkg/errors"
 	"github.com/rs/cors"
+	analytics "github.com/segmentio/analytics-go"
 	"github.com/throttled/throttled"
 	"golang.org/x/crypto/acme/autocert"
 
@@ -100,7 +101,9 @@ type Server struct {
 	clientConfig        map[string]string
 	clientConfigHash    string
 	limitedClientConfig map[string]string
-	diagnosticId        string
+
+	diagnosticId     string
+	diagnosticClient *analytics.Client
 
 	phase2PermissionsMigrationComplete bool
 
@@ -321,6 +324,11 @@ func (s *Server) Shutdown() error {
 
 	s.RunOldAppShutdown()
 
+	err := s.shutdownDiagnostics()
+	if err != nil {
+		mlog.Error(fmt.Sprintf("Unable to cleanly shutdown diagnostic client: %s", err))
+	}
+
 	s.StopHTTPServer()
 	s.WaitForGoroutines()
 
@@ -734,3 +742,30 @@ func (s *Server) StartElasticsearch() {
 		}
 	})
 }
+
+func (s *Server) initDiagnostics(endpoint string) {
+	if s.diagnosticClient == nil {
+		client := analytics.New(SEGMENT_KEY)
+		client.Logger = s.Log.StdLog(mlog.String("source", "segment"))
+		// For testing
+		if endpoint != "" {
+			client.Endpoint = endpoint
+			client.Verbose = true
+			client.Size = 1
+		}
+		client.Identify(&analytics.Identify{
+			UserId: s.diagnosticId,
+		})
+
+		s.diagnosticClient = client
+	}
+}
+
+// ShutdownDiagnostics closes the diagnostic client.
+func (s *Server) shutdownDiagnostics() error {
+	if s.diagnosticClient != nil {
+		return s.diagnosticClient.Close()
+	}
+
+	return nil
+}