git subrepo clone (merge) --branch=v3.6.1 https://github.com/nats-io/nats.c.git deps/nats.c

subrepo:
  subdir:   "deps/nats.c"
  merged:   "66cec7f"
upstream:
  origin:   "https://github.com/nats-io/nats.c.git"
  branch:   "v3.6.1"
  commit:   "66cec7f"
git-subrepo:
  version:  "0.4.6"
  commit:   "b8b46501e"

deps/nats.c/examples/getstarted/asyncsub.c

@@ -0,0 +1,69 @@
+// Copyright 2017-2018 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <nats.h>
+
+static void
+onMsg(natsConnection *nc, natsSubscription *sub, natsMsg *msg, void *closure)
+{
+    printf("Received msg: %s - %.*s\n",
+           natsMsg_GetSubject(msg),
+           natsMsg_GetDataLength(msg),
+           natsMsg_GetData(msg));
+
+    // Need to destroy the message!
+    natsMsg_Destroy(msg);
+
+    // Notify the main thread that we are done.
+    *(bool *)(closure) = true;
+}
+
+int main(int argc, char **argv)
+{
+    natsConnection      *conn = NULL;
+    natsSubscription    *sub  = NULL;
+    natsStatus          s;
+    volatile bool       done  = false;
+
+    printf("Listening on subject 'foo'\n");
+
+    // Creates a connection to the default NATS URL
+    s = natsConnection_ConnectTo(&conn, NATS_DEFAULT_URL);
+    if (s == NATS_OK)
+    {
+        // Creates an asynchronous subscription on subject "foo".
+        // When a message is sent on subject "foo", the callback
+        // onMsg() will be invoked by the client library.
+        // You can pass a closure as the last argument.
+        s = natsConnection_Subscribe(&sub, conn, "foo", onMsg, (void*) &done);
+    }
+    if (s == NATS_OK)
+    {
+        for (;!done;) {
+            nats_Sleep(100);
+        }
+    }
+
+    // Anything that is created need to be destroyed
+    natsSubscription_Destroy(sub);
+    natsConnection_Destroy(conn);
+
+    // If there was an error, print a stack trace and exit
+    if (s != NATS_OK)
+    {
+        nats_PrintLastErrorStack(stderr);
+        exit(2);
+    }
+
+    return 0;
+}