Merge pull request #17730 from lyuxuan/go_release

Add v1.18.0 releases of grpc-go to interop matrix

tools/interop_matrix/client_matrix.py

@@ -118,6 +118,7 @@ LANG_RELEASE_MATRIX = {
         ('v1.15.0', ReleaseInfo(runtime_subset=['go1.8'])),
         ('v1.16.0', ReleaseInfo(runtime_subset=['go1.8'])),
         ('v1.17.0', ReleaseInfo(runtime_subset=['go1.11'])),
+        ('v1.18.0', ReleaseInfo(runtime_subset=['go1.11'])),
     ]),
     'java':
     OrderedDict([