I also was having this error when trying to clone a repository from Github on a Windows Subsystem from Linux console:
fatal: unable to access 'http://github.com/docker/getting-started.git/': server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
The solution from @VonC on this thread didn't work for me.
The solution from this Fabian Lee's article solved it for me:
openssl s_client -showcerts -servername github.com -connect github.com:443 </dev/null 2>/dev/null | sed -n -e '/BEGIN\ CERTIFICATE/,/END\ CERTIFICATE/ p' > github-com.pem
cat github-com.pem | sudo tee -a /etc/ssl/certs/ca-certificates.crt