fix go vet issues

Author: olivere

cluster_health_test.go

@@ -17,7 +17,7 @@ func TestClusterHealth(t *testing.T) {
 		t.Fatal(err)
 	}
 	if res == nil {
-		t.Fatal("expected res to be != nil; got: %v", res)
+		t.Fatalf("expected res to be != nil; got: %v", res)
 	}
 	if res.Status != "green" {
 		t.Fatalf("expected status %q; got: %q", "green", res.Status)

cluster_state_test.go

@@ -17,7 +17,7 @@ func TestClusterState(t *testing.T) {
 		t.Fatal(err)
 	}
 	if res == nil {
-		t.Fatal("expected res to be != nil; got: %v", res)
+		t.Fatalf("expected res to be != nil; got: %v", res)
 	}
 	if res.ClusterName == "" {
 		t.Fatalf("expected a cluster name; got: %q", res.ClusterName)

example_test.go

@@ -425,7 +425,7 @@ func ExampleClusterHealthService() {
 	if res == nil {
 		panic(err)
 	}
-	fmt.Println("Cluster status is %q", res.Status)
+	fmt.Printf("Cluster status is %q\n", res.Status)
 }
 
 func ExampleClusterHealthService_WaitForGreen() {