[go] Update go toolset 1.11.1 => 1.11.5.

Let's use latest toolchain.

Change-Id: Iaddb0895db758b75d1b9945d5f16931772ea2db1
Reviewed-on: https://chromium-review.googlesource.com/c/1457257
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#20516}
diff --git a/go/bootstrap.py b/go/bootstrap.py
index e3f13e2..1e69048 100755
--- a/go/bootstrap.py
+++ b/go/bootstrap.py
@@ -46,7 +46,7 @@
 GIT_EXE = 'git.bat' if sys.platform == 'win32' else 'git'
 
 # Version of Go toolset CIPD package (infra/go/${platform}) to install.
-TOOLSET_VERSION = '1.11.1'
+TOOLSET_VERSION = '1.11.5'
 
 # Describes how to fetch 'glide'.
 GLIDE_SOURCE = {