code: func pickSASLMechanism(client []Authentication, serverMechanisms []string) (auth Authentication, ok bool) {
  	for _, auth = range client {
  		for _, mech := range serverMechanisms {
  			if auth.Mechanism() == mech {
  				return auth, true
  			}
  		}
  	}
  
  	return
  }
docs: // Finds the first mechanism preferred by the client that the server supports.