Use Apple internal type for timeout

src/objective-c/GRPCClient/GRPCCall.h

@@ -172,7 +172,7 @@ extern id const kGRPCTrailersKey;
 /**
  * The timeout for the RPC call in milliseconds. If set to 0, the call will not timeout.
  */
-@property UInt64 timeout;
+@property NSTimeInterval timeout;
 
 /**
  * The container of the request headers of an RPC conforms to this protocol, which is a subset of

src/objective-c/GRPCClient/private/GRPCChannel.h

@@ -63,6 +63,6 @@ struct grpc_channel_credentials;
 
 - (nullable grpc_call *)unmanagedCallWithPath:(nonnull NSString *)path
                                    serverName:(nonnull NSString *)serverName
-                                      timeout:(UInt64)timeout
+                                      timeout:(NSTimeInterval)timeout
                               completionQueue:(nonnull GRPCCompletionQueue *)queue;
 @end

src/objective-c/GRPCClient/private/GRPCChannel.m

@@ -182,7 +182,7 @@ static grpc_channel_args *BuildChannelArgs(NSDictionary *dictionary) {
 
 - (grpc_call *)unmanagedCallWithPath:(NSString *)path
                           serverName:(NSString *)serverName
-                             timeout:(UInt64)timeout
+                             timeout:(NSTimeInterval)timeout
                      completionQueue:(GRPCCompletionQueue *)queue {
   grpc_slice host_slice;
   if (serverName) {
@@ -193,7 +193,7 @@ static grpc_channel_args *BuildChannelArgs(NSDictionary *dictionary) {
                                 gpr_inf_future(GPR_CLOCK_REALTIME) :
                                 gpr_time_add(
                                     gpr_now(GPR_CLOCK_MONOTONIC),
-                                    gpr_time_from_millis(timeout, GPR_TIMESPAN));
+                                    gpr_time_from_millis((int64_t)(timeout * 1000), GPR_TIMESPAN));
   grpc_call *call = grpc_channel_create_call(_unmanagedChannel,
                                              NULL, GRPC_PROPAGATE_DEFAULTS,
                                              queue.unmanagedQueue,

src/objective-c/GRPCClient/private/GRPCHost.h

@@ -55,7 +55,7 @@ struct grpc_channel_credentials;
 /** Create a grpc_call object to the provided path on this host. */
 - (nullable struct grpc_call *)unmanagedCallWithPath:(NSString *)path
                                           serverName:(NSString *)serverName
-                                             timeout:(UInt64)timeout
+                                             timeout:(NSTimeInterval)timeout
                                      completionQueue:(GRPCCompletionQueue *)queue;
 
 // TODO: There's a race when a new RPC is coming through just as an existing one is getting

src/objective-c/GRPCClient/private/GRPCHost.m

@@ -121,7 +121,7 @@ static GRPCConnectivityMonitor *connectivityMonitor = nil;
 
 - (nullable grpc_call *)unmanagedCallWithPath:(NSString *)path
                                    serverName:(NSString *)serverName
-                                      timeout:(UInt64)timeout
+                                      timeout:(NSTimeInterval)timeout
                               completionQueue:(GRPCCompletionQueue *)queue {
   GRPCChannel *channel;
   // This is racing -[GRPCHost disconnect].

src/objective-c/GRPCClient/private/GRPCWrappedCall.h

@@ -77,7 +77,7 @@
 - (instancetype)initWithHost:(NSString *)host
                   serverName:(NSString *)serverName
                         path:(NSString *)path
-                     timeout:(UInt64)timeout NS_DESIGNATED_INITIALIZER;
+                     timeout:(NSTimeInterval)timeout NS_DESIGNATED_INITIALIZER;
 
 - (void)startBatchWithOperations:(NSArray *)ops errorHandler:(void(^)())errorHandler;
 

src/objective-c/GRPCClient/private/GRPCWrappedCall.m

@@ -244,7 +244,7 @@
 - (instancetype)initWithHost:(NSString *)host
                   serverName:(NSString *)serverName
                         path:(NSString *)path
-                     timeout:(UInt64)timeout {
+                     timeout:(NSTimeInterval)timeout {
   if (!path || !host) {
     [NSException raise:NSInvalidArgumentException
                 format:@"path and host cannot be nil."];