Erroneous 'Ignored LSP error: nil'

[sqs]

After running lsp-mode-init-conn and connecting successfully to the Go lang server (installed with go get -u github.com/sourcegraph/go-langserver/langserver/cmd/langserver-go), I see the following error in emacs *Messages*:

Ignored LSP error: nil

There doesn't seem to be any error: it says "nil", which shouldn't indicate an error, and the lang server doesn't show any errors. Here is the trace output from langserver-go:

$ langserver-go -mode tcp -trace
langserver-go: listening on :4389
--> request #1329760234113517669: initialize: {"capabilities":null,"processId":null,"rootPath":"/home/sqs/src/github.com/sourcegraph/jsonrpc2/","initializationOptions":null}
<-- result #1329760234113517669: initialize: {"capabilities":{"textDocumentSync":1,"hoverProvider":true,"definitionProvider":true,"referencesProvider":true,"documentSymbolProvider":true,"workspaceSymbolProvider":true}}
--> request #1369339415339987355: textDocument/didOpen: {"textDocument":{"uri":"file:///home/sqs/src/github.com/sourcegraph/jsonrpc2/jsonrpc2.go"}}
<-- result #1369339415339987355: textDocument/didOpen: {}