don't fail setup if go help mod fails

script/source-setup/go

@@ -20,8 +20,12 @@ if [ "$1" == "-f" ]; then
     -and -not -path "*/src" \
     -print0 | xargs -0 rm -rf
 
-  go help mod >/dev/null && go clean -modcache
+  if go help mod >/dev/null; then
+    go clean -modcache
+  fi
 fi
 
 (cd src/test && go get)
-go help mod >/dev/null && (cd src/modules_test && GO111MODULE=on go mod download)
+if go help mod >/dev/null; then
+  (cd src/modules_test && GO111MODULE=on go mod download)
+fi