Getting data from UniProt-GOA
Every month, UniProt-GOA produces gene association files containing all of the available GO annotations for UniProtKB proteins. The 'UniProt' file contains GO annotations for proteins from all species in UniProtKB. There are also a number of species-specific files which contain GO annotations for certain species that have a complete proteome, such as human, mouse, Arabidopsis, yeast, zebrafish, etc.
The UniProt-GOA gene association files are available from the download page on the UniProt-GOA website, and previous versions of the gene association files are also available from the UniProt-GOA ftp site.