I don't know if the government of any African country have adopted the system of paying salaries in Bitcoin, but I know here is Nigeria they haven't, it's possible to pay employees using Bitcoin or other crypto currencies ,
With the services of some crypto currency payroll agencies  like Bitwage,papaya global, ontop,  which will make it possible for the government to pay their workers in Bitcoin or other crypto currencies and can be sent  into their digital wallet,
Since it has to do with the government another agency can be set up in the country in respect to paying salaries as Bitcoin which will somehow help in the growth of the economy of the country.