Debian/Ubuntu 对gpg和apt-key使用代理–报错解决：gpg: keyserver receive failed: Connection timed out

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
Executing: /tmp/apt-key-gpghome.SLXjdH01xN/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5

gpg: keyserver receive failed: Connection timed out

gpg和apt-key使不会直接读取终端中设置的代理，需要单独设置。所以要单独地设置代理 --keyserver-options http-proxy=$http_proxy

sudo apt-key adv --keyserver-options http-proxy=$http_proxy --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5