Waiting for another flutter command to release the startup lock

flutter lockfile

In my case, following command in Terminal helped (as suggested by Günter):

killall -9 dart

On Windows (as suggested by upupming):

taskkill /F /IM dart.exe

flutter lockfile

Remove this file:

<YOUR FLUTTER FOLDER>/bin/cache/lockfile

This releases the occupied lock and makes you able to run other commands.

flutter lockfile

I use a Mac with Visual Studio Code and this is what worked:

Shutdown your PC and switch it on again. Don't use the restart function. I restarted 2 times and it didn't work. Only shutdown worked.

PS: I tried out the following:

But they all didn't work.

CodeHunter