package/go: bump to version 1.15.6

go1.15.6 (released 2020/12/03) includes fixes to the compiler, linker, runtime,
the go command, and the io package.

Signed-off-by: Christian Stewart <christian@paral.in>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/go/go.hash

@@ -1,3 +1,3 @@
 # From https://golang.org/dl/
-sha256  c1076b90cf94b73ebed62a81d802cd84d43d02dea8c07abdc922c57a071c84f1  go1.15.5.src.tar.gz
+sha256  890bba73c5e2b19ffb1180e385ea225059eb008eb91b694875dd86ea48675817  go1.15.6.src.tar.gz
 sha256	2d36597f7117c38b006835ae7f537487207d8ec407aa9d9980794b2030cbc067  LICENSE

package/go/go.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GO_VERSION = 1.15.5
+GO_VERSION = 1.15.6
 GO_SITE = https://storage.googleapis.com/golang
 GO_SOURCE = go$(GO_VERSION).src.tar.gz