terraform-lsp can be used with CoC.
Install the terraform-lsp binary and verify it's available in your $PATH.
Go to your coc-settings.json file (you can use the following command in Vim: :CocConfig).
Add an entry for the terraform language server.
{
"languageserver": {
"terraform": {
"command": "terraform-lsp",
"filetypes": ["terraform"]
}
}
}