Waiting for another flutter comm

更新flutter，执行命令

flutter upgrade

提示

Waiting for another flutter command to release the startup lock...

这是其他地方正在用到flutter命令，可以等待一会自己执行结束。
也可以删除你的flutter sdk目录下的bin/cache/lockfile 文件进行删除。然后重新执行 flutter upgrade