code: func (c *Context) VerifySelectiveFlags(flags uint32) error {
  	if valid, missing, extra := verifySelectiveFlags(flags, c.RequestedFlags); !valid {
  		return fmt.Errorf("sspi: invalid flags check: desired=%b requested=%b missing=%b extra=%b", flags, c.RequestedFlags, missing, extra)
  	}
  	if valid, missing, extra := verifySelectiveFlags(flags, c.EstablishedFlags); !valid {
  		return fmt.Errorf("sspi: invalid flags: desired=%b established=%b missing=%b extra=%b", flags, c.EstablishedFlags, missing, extra)
  	}
  	return nil
  }
docs: // VerifySelectiveFlags determines if the given flags were honored (see NewClientContext).
  // It should be called after c.Update.