remove travis.yml, Go 1.16

We no longer need TravisCI, at least not in any component branch which
uses csi-release-tools master. Therefore we can remove it and make
prow.sh the authoritative source for the intended Go version.

While doing that, the version of Go gets bumped to 1.16 (same as
Kubernetes 1.21).

Author: pohly

Diff for: README.md

@@ -21,7 +21,11 @@ The expected repository layout is:
    Dockerfile in the root when only building a single command
  - `Makefile` - includes `release-tools/build.make` and sets
    configuration variables
- - `.travis.yml` - a symlink to `release-tools/.travis.yml`
+ - `.prow.sh` script which imports `release-tools/prow.sh`
+   and may contain further customization
+ - `.cloudbuild.sh` and `cloudbuild.yaml` as symlinks to
+   the corresponding files in `release-tools` or (if necessary)
+   as custom files
 
 To create a release, tag a certain revision with a name that
 starts with `v`, for example `v1.0.0`, then `make push`

Diff for: cloudbuild.yaml

@@ -25,7 +25,7 @@ options:
   substitution_option: ALLOW_LOOSE
 steps:
   # The image must contain bash and curl. Ideally it should also contain
-  # the desired version of Go (currently defined in release-tools/travis.yml),
+  # the desired version of Go (currently defined in release-tools/prow.sh),
   # but that just speeds up the build and is not required.
   - name: 'gcr.io/k8s-testimages/gcb-docker-gcloud:v20200421-a2bf5f8'
     entrypoint: ./.cloudbuild.sh

Diff for: prow.sh

@@ -85,14 +85,7 @@ configvar CSI_PROW_BUILD_PLATFORMS "linux amd64; windows amd64 .exe; linux ppc64
 # which is disabled with GOFLAGS=-mod=vendor).
 configvar GOFLAGS_VENDOR "$( [ -d vendor ] && echo '-mod=vendor' )" "Go flags for using the vendor directory"
 
-# Go versions can be specified separately for different tasks
-# If the pre-installed Go is missing or a different
-# version, the required version here will get installed
-# from https://golang.org/dl/.
-go_from_travis_yml () {
-    grep "^ *- go:" "${RELEASE_TOOLS_ROOT}/travis.yml" | sed -e 's/.*go: *//'
-}
-configvar CSI_PROW_GO_VERSION_BUILD "$(go_from_travis_yml)" "Go version for building the component" # depends on component's source code
+configvar CSI_PROW_GO_VERSION_BUILD "1.16" "Go version for building the component" # depends on component's source code
 configvar CSI_PROW_GO_VERSION_E2E "" "override Go version for building the Kubernetes E2E test suite" # normally doesn't need to be set, see install_e2e
 configvar CSI_PROW_GO_VERSION_SANITY "${CSI_PROW_GO_VERSION_BUILD}" "Go version for building the csi-sanity test suite" # depends on CSI_PROW_SANITY settings below
 configvar CSI_PROW_GO_VERSION_KIND "${CSI_PROW_GO_VERSION_BUILD}" "Go version for building 'kind'" # depends on CSI_PROW_KIND_VERSION below

Diff for: travis.yml

@@ -29,8 +29,9 @@ die () {
 version=$("$GO" version) || die "determining version of $GO failed"
 # shellcheck disable=SC2001
 majorminor=$(echo "$version" | sed -e 's/.*go\([0-9]*\)\.\([0-9]*\).*/\1.\2/')
-# shellcheck disable=SC2001
-expected=$(grep "^ *- go:" "release-tools/travis.yml" | sed -e 's/.*go: *\([0-9]*\)\.\([0-9]*\).*/\1.\2/')
+# SC1091: Not following: release-tools/prow.sh was not specified as input (see shellcheck -x).
+# shellcheck disable=SC1091
+expected=$(. release-tools/prow.sh && echo "$$CSI_PROW_GO_VERSION_BUILD")
 
 if [ "$majorminor" != "$expected" ]; then
     cat >&2 <<EOF