(vsCode) Unable to resolve assembly ~~

Unity  2019.3.4f1 personal
vsCode 1.43.2

so many warnings
 Unable to resolve assembly '~~~.dll'

There are a few solutions , in my case installing older version of the c# extension of vsCode works.

 But, I don't know why c# 1.21.15 being showed on installed extensions.
I've downloaded 1.21.12 version manually and install.
'Debugger for Unity' is dependent on c# extension, so you should uninstall it first.






 After that, received many message from git.