Log:
E:\Flutter>flutter doctor Checking Dart SDK version… Downloading
Dart SDK from Flutter engine ead227f a… Unzipping Dart SDK…
Updating flutter tool… Error: Unable to 'pub upgrade' flutter tool.
Retrying in five seconds…Waiting for 0 seconds, press CTRL+C to quit … Error: Unable to 'pub
upgrade' flutter tool. Retrying in five seconds…Waiting for 0 seconds, press CTRL+C to quit … Error: Unable to 'pub
upgrade' flutter tool. Retrying in five seconds…Waiting for 0 seconds, press CTRL+C to quit … Error: Unable to 'pub
upgrade' flutter tool. Retrying in five seconds…Waiting for 0 seconds, press CTRL+C to quit … Error: Unable to 'pub
upgrade' flutter tool. Retrying in five seconds…Waiting for 0 seconds, press CTRL+C to quit … Error: Unable to 'pub
upgrade' flutter tool. Retrying in five seconds…
Best Solution
First Make sure you have a working internet connection and if this issue still exists then, this error may be because the dart sdk may have not been properly downloaded. The simplest solution is to delete the
cachefolder located influtter/bin(location where flutter is installed) and then Runflutter doctor