Add channel args to enable user agent string for Objective-C
diff --git a/examples/objective-c/helloworld/main.m b/examples/objective-c/helloworld/main.m
index a62f836..f390b5a 100644
--- a/examples/objective-c/helloworld/main.m
+++ b/examples/objective-c/helloworld/main.m
@@ -34,6 +34,7 @@
 #import <UIKit/UIKit.h>
 #import "AppDelegate.h"
 
+#import <GRPCClient/GRPCCall+ChannelArg.h>
 #import <GRPCClient/GRPCCall+Tests.h>
 #import <HelloWorld/Helloworld.pbrpc.h>
 
@@ -42,6 +43,7 @@
 int main(int argc, char * argv[]) {
   @autoreleasepool {
     [GRPCCall useInsecureConnectionsForHost:kHostAddress];
+    [GRPCCall usePrimaryUserAgent:@"HelloWorld/1.0" forHost:kHostAddress];
 
     HLWGreeter *client = [[HLWGreeter alloc] initWithHost:kHostAddress];