package/go: security bump to version 1.15.13

Fixes the following security issues:

- CVE-2021-33195: The LookupCNAME, LookupSRV, LookupMX, LookupNS, and
  LookupAddr functions in net, and their respective methods on the Resolver
  type may return arbitrary values retrieved from DNS which do not follow
  the established RFC 1035 rules for domain names.  If these names are used
  without further sanitization, for instance unsafely included in HTML, they
  may allow for injection of unexpected content.  Note that LookupTXT may
  still return arbitrary values that could require sanitization before
  further use

- CVE-2021-33196: The NewReader and OpenReader functions in archive/zip can
  cause a panic or an unrecoverable fatal error when reading an archive that
  claims to contain a large number of files, regardless of its actual size

- CVE-2021-33197: ReverseProxy in net/http/httputil could be made to forward
  certain hop-by-hop headers, including Connection.  In case the target of
  the ReverseProxy was itself a reverse proxy, this would let an attacker
  drop arbitrary headers, including those set by the ReverseProxy.Director

- CVE-2021-33198: The SetString and UnmarshalText methods of math/big.Rat
  may cause a panic or an unrecoverable fatal error if passed inputs with
  very large exponents

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

package/go/go.hash

@@ -1,3 +1,3 @@
 # From https://golang.org/dl/
-sha256  1c6911937df4a277fa74e7b7efc3d08594498c4c4adc0b6c4ae3566137528091  go1.15.12.src.tar.gz
+sha256  99069e7223479cce4553f84f874b9345f6f4045f27cf5089489b546da619a244  go1.15.13.src.tar.gz
 sha256	2d36597f7117c38b006835ae7f537487207d8ec407aa9d9980794b2030cbc067  LICENSE

package/go/go.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GO_VERSION = 1.15.12
+GO_VERSION = 1.15.13
 GO_SITE = https://storage.googleapis.com/golang
 GO_SOURCE = go$(GO_VERSION).src.tar.gz