See apt-secure(8) manpage for re

参考了：https://stackoverflow.com/questions/59139453/repository-is-not-signed-in-docker-build
我尝试在docker中执行 RUN apt-get update && apt-get install -y openssh-server，但总是得到下面的异常：

Get:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease [108 kB]
Err:3 http://archive.ubuntu.com/ubuntu focal-updates InRelease
 At least one invalid signature was encountered.
Err:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease
 At least one invalid signature was encountered.
Reading package lists... Done
W: GPG error: http://security.ubuntu.com/ubuntu focal-security InRelease: At least one invalid signature was encountered.
E: The repository 'http://security.ubuntu.com/ubuntu focal-security InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://archive.ubuntu.com/ubuntu focal InRelease: At least one invalid signature was encountered.
E: The repository 'http://archive.ubuntu.com/ubuntu focal InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://archive.ubuntu.com/ubuntu focal-updates InRelease: At least one invalid signature was encountered.
E: The repository 'http://archive.ubuntu.com/ubuntu focal-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://archive.ubuntu.com/ubuntu focal-backports InRelease: At least one invalid signature was encountered.
E: The repository 'http://archive.ubuntu.com/ubuntu focal-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.