What version of Go are you using (go version)?

go version go1.10.3 linux/amd64

Does this issue reproduce with the latest release?

Yes, and on master.

What did you do?

In a terminal:

$ cp /dev/null ./index
$ godoc -http=:6060 -index -index_files=./index
2018/06/23 13:21:03 error reading index from file ./index: EOF

Requests made to the godoc HTTP server will fail. The error message is printed by Corpus.RunIndexer(), and with the combination of flags listed above the index will never be re-checked.

In another terminal:

$ godoc -write_index -index_files=./index

After this process completes there is a valid index file for the HTTP server. However, index search requests will still fail, as the HTTP server will not try to re-initialize the index. There is no mechanism to ask the HTTP server to reload the index other than restarting the godoc process.

What did you expect to see?

I expect the index to service queries once the index file becomes valid.

My proposed semantics: if -index and -index_files are both specified but the index is in an uninitialized state, search queries should try to re-initialize the index. This would cause the index to be checked on every query until the index can be successfully loaded.