It's really frustrating, wasted 3 days to get rid of but still on stuck problem showing on macos catalina version 10.15.1 and windows 7 also. My two PC's showing same error. First when i tried to 'get packages'
it's showing this '/Users/mamun/Developer/flutter/bin/flutter --no-color packages get Waiting for another flutter command to release the startup lock...'
after few moments it's showing..
'/Users/mamun/Developer/flutter/bin/flutter --no-color packages get
Running "flutter pub get" in flutterx...
Connection terminated during handshake
pub get failed (server unavailable) -- attempting retry 1 in 1 second...
Connection terminated during handshake
pub get failed (server unavailable) -- attempting retry 2 in 2 seconds...,
tried this Waiting for another flutter command to release the startup lock
This is a country-specific problem. In some countries, you got this error like Bangladesh and some African countries. I got a solution to this problem, that is use VPN software when you want to get Packages. VPN software uses other country's IP addresses where this google service works perfectly, So you can easily download packages.