Find References (Ctrl+Shift+G) must be executed several times

[angelozerr]

Find References (Ctrl+Shift+G) doesn't work if tsserver is not started. It should be executed several times and search result works when tsserver is started. It' snot user friendly. Fix this problem by managing the timeout.

[angelozerr]

Fixed since Java8 CompletableFuture are used now.