internal/lsp: include context in go/packages config
internal/lsp: include context in go/packages config

Include the context when invoking go/packages.Load so it is
cancelable. Otherwise if the user is manually typing an import or
otherwise messing around with imports, a big queue of potentially very
slow go/packages.Load calls will build up.

Fixes golang/go#34414.

Change-Id: I80732086b478b908c720739708dd773e81fe2b81
Reviewed-on: https://go-review.googlesource.com/c/tools/+/200058
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
Reviewed-by: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools