debug: support logging to a file with dlv-dap

[polinasok]

With certain "trace" attribute settings, the legacy adapter prints:

Verbose logs are written to:
/var/folders/dn/8hszkj9x21n__1gr_p8qgjgr0007jz/T/vscode-go-debug.txt

That's very convenient.
Can we set up trace for dlv-dap to capture whatever we get from dlv-dap and not just write it to debug console, but also write to a file?

[hyangah]

Thanks for filing the issue. I hoped we could've used --log-dest flag of delve but unfortunately, that breaks the current dlv-dap integration. The plan I had is to pass a file descriptor to --log-dest, and process the stream while teeing the logging info to user-specified file (if any). That way, we can also avoid crowding the DEBUG OUTPUT with the logging messages.

[gopherbot]

Change https://golang.org/cl/313050 mentions this issue: src/goDebugFactory: use --log-dest to capture dlv logs and add logDest

[gopherbot]

Change https://golang.org/cl/317290 mentions this issue: src/goDebugFactory: disable logDest support on windows