by anu.engineer:

if you ask for  Extended Key Usage in Certificates with the following Flags 
- ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth |
x509.ExtKeyUsageClientAuth}, CreateCertificate code generates "Code Signing"
instead of the expected ServerAuth | ClientAuth in the Certificate.

Please see the Line 69 in the code , this is a code sample modified from GO distribution
with only one line modification 

+ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth |
x509.ExtKeyUsageClientAuth}, 

http://play.golang.org/p/vpvoNPNlJU

it was executed with following command

./certgen -host=anu.engineer.com -ca=true -duration=8760h0m0s -rsa-bits=2048
-start-date="Mar 11 00:00:00 2014"  

and when viewed with OpenSSL the certificate has the following fields
aengineer$ openssl x509 -in cert.pem -text

<<snip>>

 X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment, Certificate Sign
            X509v3 Extended Key Usage: 
                Code Signing
            X509v3 Basic Constraints: critical
                CA:TRUE
            X509v3 Subject Alternative Name: 
                DNS:anu.engineer.com
<<snip>>
Expected Values 
            X509v3 Extended Key Usage: 
                Server Auth, Client Auth