package/go: security bump to version 1.11.13

From the release notes:

- go1.11.10 (released 2019/05/06) includes fixes to the runtime and the
  linker

- go1.11.11 (released 2019/06/11) includes a fix to the crypto/x509 package

- go1.11.12 (released 2019/07/08) includes fixes to the compiler and the
  linker

- go1.11.13 (released 2019/08/13) includes security fixes to the net/http
  and net/url packages

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/go/go.hash

@@ -1,3 +1,3 @@
 # From https://golang.org/dl/
-sha256	ee80684b352f8d6b49d804d4e615f015ae92da41c4096cfee89ed4783b2498e3  go1.11.9.src.tar.gz
+sha256	5032095fd3f641cafcce164f551e5ae873785ce7b07ca7c143aecd18f7ba4076  go1.11.13.src.tar.gz
 sha256	2d36597f7117c38b006835ae7f537487207d8ec407aa9d9980794b2030cbc067  LICENSE

package/go/go.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GO_VERSION = 1.11.9
+GO_VERSION = 1.11.13
 GO_SITE = https://storage.googleapis.com/golang
 GO_SOURCE = go$(GO_VERSION).src.tar.gz