It is maintained by Google and the whole go community since it is in the standard library. So, I think it is fairly secure (probably not as well tested as OpenSSL but the attack surface is smaller, bugs and security risks are still there, though).<p>What is important is that the library is not hardware accelerated and it thus uses a software accelerated AES cipher. 
So, I think it is a bit slower, but you would really have to measure it yourself.<p>Upgrading your Load balancer should not be that hard, though.