pubsub: release v1.2.0

This PR will be tagged pubsub/v1.2.0.

Change-Id: If788320ceb80aeb05ff548c41a046d4f59c28d15
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/51390
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Seth Hollyman <shollyman@google.com>
Reviewed-by: Chris Broadfoot <cbro@google.com>
diff --git a/internal/version/version.go b/internal/version/version.go
index 56ca2c9..1caf584 100644
--- a/internal/version/version.go
+++ b/internal/version/version.go
@@ -26,7 +26,7 @@
 
 // Repo is the current version of the client libraries in this
 // repo. It should be a date in YYYYMMDD format.
-const Repo = "20200128"
+const Repo = "20200202"
 
 // Go returns the Go runtime version. The returned string
 // has no whitespace.
diff --git a/pubsub/CHANGES.md b/pubsub/CHANGES.md
index c9a92f1..0ea76a5 100644
--- a/pubsub/CHANGES.md
+++ b/pubsub/CHANGES.md
@@ -1,5 +1,15 @@
 # Changes
 
+## v1.2.0
+
+- Add support for upcoming dead letter topics feature
+- Expose Subscription.ReceiveSettings.MaxExtensionPeriod setting
+- Standardize default settings with other client libraries
+  - Increase publish delay threshold from 1ms to 10ms
+  - Increase subscription MaxExtension from 10m to 60m
+- Always send keepalive/heartbeat ping on StreamingPull streams to minimize
+  stream reopen requests
+
 ## v1.1.0
 
 - Limit default grpc connections to 4.