ci: upgrade to use Go 1.16.7 (#10856)

.changelog/10856.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+ci: upgrade to use Go 1.16.7
+```

.circleci/config.yml

@@ -15,7 +15,7 @@ references:
   images:
     # When updating the Go version, remember to also update the versions in the
     # workflows section for go-test-lib jobs.
-    go: &GOLANG_IMAGE docker.mirror.hashicorp.services/circleci/golang:1.16.3
+    go: &GOLANG_IMAGE docker.mirror.hashicorp.services/circleci/golang:1.16.7
     ember: &EMBER_IMAGE docker.mirror.hashicorp.services/circleci/node:14-browsers
 
   paths:

build-support/docker/Build-Go.dockerfile

@@ -1,4 +1,4 @@
-ARG GOLANG_VERSION=1.15.5
+ARG GOLANG_VERSION=1.16.7
 FROM golang:${GOLANG_VERSION}
 
 ARG GOTOOLS="github.com/elazarl/go-bindata-assetfs/... \

build-support/docker/Test-Flake.dockerfile

@@ -1,6 +1,6 @@
 FROM travisci/ci-garnet:packer-1512502276-986baf0
 
-ENV GOLANG_VERSION 1.15.5
+ENV GOLANG_VERSION 1.16.7
 
 RUN mkdir -p /home/travis/go && chown -R travis /home/travis/go