Revert "Revert "Add OAuth2 protocol in GRPCClient""
diff --git a/templates/gRPC.podspec.template b/templates/gRPC.podspec.template
index 62a6d37..5c92f9f 100644
--- a/templates/gRPC.podspec.template
+++ b/templates/gRPC.podspec.template
@@ -42,12 +42,9 @@
     s.header_dir = name
 
     src_dir = 'src/objective-c/GRPCClient'
-    s.source_files = "#{src_dir}/*.{h,m}", "#{src_dir}/**/*.{h,m}"
-    s.private_header_files = "#{src_dir}/private/*.h"
-    s.header_mappings_dir = "#{src_dir}"
 
-    s.dependency 'gRPC-Core', version
     s.dependency 'gRPC-RxLibrary', version
+    s.default_subspec = 'Main'
 
     # Certificates, to be able to establish TLS connections:
     s.resource_bundles = { 'gRPCCertificates' => ['etc/roots.pem'] }
@@ -56,4 +53,22 @@
       # This is needed by all pods that depend on gRPC-RxLibrary:
       'CLANG_ALLOW_NON_MODULAR_INCLUDES_IN_FRAMEWORK_MODULES' => 'YES',
     }
+
+    s.subspec 'Main' do |ss|
+      ss.header_mappings_dir = "#{src_dir}"
+
+      ss.source_files = "#{src_dir}/*.{h,m}", "#{src_dir}/**/*.{h,m}"
+      ss.exclude_files = "#{src_dir}/GRPCCall+GID.{h,m}"
+      ss.private_header_files = "#{src_dir}/private/*.h"
+
+      ss.dependency 'gRPC-Core', version
+    end
+
+    s.subspec 'GID' do |ss|
+      ss.header_mappings_dir = "#{src_dir}"
+
+      ss.source_files = "#{src_dir}/GRPCCall+GID.{h,m}"
+
+      ss.dependency 'Google/SignIn'
+    end
   end