Squashed 'release-tools/' changes from 98f23071..406a79ac

406a79ac Merge pull request kubernetes-csi#267 from huww98/gomodcache
9cec273d Set GOMODCACHE to avoid re-download toolchain

git-subtree-dir: release-tools
git-subtree-split: 406a79acf021b5564108afebeea7d0ed44648d3f

prow.sh

@@ -441,7 +441,8 @@ run_with_go () {
     else
         version=local
     fi
-    GOTOOLCHAIN=$version run "$@"
+    # Set GOMODCACHE to make sure Kubernetes does not need to download again.
+    GOTOOLCHAIN=$version GOMODCACHE="$(go env GOMODCACHE)" run "$@"
 }
 
 # Ensure that we have the desired version of kind.