Log Message:
gopls: update to 0.4.4.

* Support for opening a single file. Previously, gopls required
  you to open an entire directory.
* Support features and diagnostics for the entire module, even when
  you open a subdirectory of the module.
* Extract a selected range to a variable or to a function. This
  feature is still relatively new, so please report issues if you
  encounter any. (@joshbaum)
* Fillstruct performance improvements. It is now enabled by default
  again. (@joshbaum)
* Improvements in go.mod diagnostic error presentation.