Line numbers are off by one

[sqs]

See cursor position is on callOptionFunc but the hover string (in the way bottom) is for SetMeta, which is on the line below.

The Go lang server trace shows:

$ langserver-go -mode tcp -trace
langserver-go: listening on :4389
--> request #1071513773664973755: initialize: {"capabilities":null,"processId":null,"rootPath":"/home/sqs/src/github.com/sourcegraph/jsonrpc2/","initializationOptions":null}
<-- result #1071513773664973755: initialize: {"capabilities":{"textDocumentSync":1,"hoverProvider":true,"definitionProvider":true,"referencesProvider":true,"documentSymbolProvider":true,"workspaceSymbolProvider":true}}
...
--> request #79049804191771228: textDocument/hover: {"textDocument":{"uri":"file:///home/sqs/src/github.com/sourcegraph/jsonrpc2/call_opt.go"},"position":{"line":17,"character":16}}
<-- result #79049804191771228: textDocument/hover: {"contents":[{"language":"go","value":"func (*Request).SetMeta(v interface{}) error"},{"language":"markdown","value":"SetMeta sets r.Meta to the JSON representation of v. If JSON marshaling fails, it returns an error. \n\n"}],"range":{"start":{"line":17,"character":11},"end":{"line":17,"character":18}}}

See that the textDocument/hover request's line is 17 (which is indeed the line number if you are counting line numbers starting at 1). Per the LSP spec (https://github.com/Microsoft/language-server-protocol/blob/master/protocol.md#position), the line number is zero-based. This means that the request should have asked for line 16, not 17.

• Send zero-based line number
• The column number is ALSO 0-based, so the same adjustment needs to be applied to make the column number zero-based.
• When the LSP adapter gets an LSP response with a position, it needs to convert the zero-based response data to 1-indexed numbers for Emacs.

(Note: I was only able to get this to work by hackily removing all calls to textDocument/didOpen, as necessitated by #5. So, you should fix that before this.)