test.bash: update to go1.10.4 and go1.11.1 for v1 branch

Change-Id: I48f723a41c9d452167509a0d7be42ba72c8e3ac8
Reviewed-on: https://go-review.googlesource.com/c/145659
Reviewed-by: Joe Tsai <joetsai@google.com>

test.bash

@@ -37,8 +37,8 @@ mkdir -p $PROTOBUF_DIR/src/include
 ln -s ../google $PROTOBUF_DIR/src/include/google
 
 # Download each Go toolchain version.
-GO_LATEST=go1.11
-GO_VERSIONS=(go1.9.7 go1.10.3 $GO_LATEST)
+GO_LATEST=go1.11.1
+GO_VERSIONS=(go1.9.7 go1.10.4 $GO_LATEST)
 for GO_VERSION in ${GO_VERSIONS[@]}; do
 	if [ ! -d $GO_VERSION ]; then
 		print "download $GO_VERSION"