Error: Error parsing : unexpected token while parsing list: IDENT

while using reference expression to link service group id to instance vpc security group getting this error

Without seeing the relevant code and the exact error message I can only guess here, but I expect you probably have a configuration that is using features that are available only in Terraform 0.12 or later but you are running Terraform 0.11 or earlier. That tends to cause errors like this, because those new 0.12 features are not recognized by the Terraform 0.11 configuration parser.