all: update to go1.13.12 and go1.14.4

Change-Id: I38b18cf8124fcc52d56741e0cefb68fe973ab087
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/238758
Reviewed-by: Herbie Ong <herbie@google.com>
diff --git a/integration_test.go b/integration_test.go
index 721aec9..54ad30f 100644
--- a/integration_test.go
+++ b/integration_test.go
@@ -36,7 +36,7 @@
 	protobufVersion = "ef7cc811" // v3.12.0-rc1
 	protobufSHA256  = ""         // ignored if protobufVersion is a git hash
 
-	golangVersions = []string{"1.9.7", "1.10.8", "1.11.13", "1.12.17", "1.13.11", "1.14.3"}
+	golangVersions = []string{"1.9.7", "1.10.8", "1.11.13", "1.12.17", "1.13.12", "1.14.4"}
 	golangLatest   = golangVersions[len(golangVersions)-1]
 
 	staticcheckVersion = "2020.1.4"