Keyserver refresh failed: Server indicated a failure

I tried to install swift 5 in my ubuntu 18.04
the used the command below to refresh the key:
gpg --keyserver hkp://pool.sks-keyservers.net --refresh-keys Swift

but i got these lines of error message:
gpg: refreshing 3 keys from hkp://pool.sks-keyservers.net
gpg: keyserver refresh failed: Server indicated a failure

what can i do now?