coc-settings.json

{
  "diagnostic.virtualText": true,

  "coc.preferences.currentFunctionSymbolAutoUpdate": true,

  "suggest.enablePreview": true,
  "suggest.enablePreselect": false,

  "codeLens.enable": true,

  "coc.preferences.formatOnSaveFiletypes": ["go", "elm"],

  "languageserver": {
    "elmLS": {
      "command": "elm-language-server",
      "args": ["--stdio"],
      "filetypes": ["elm"],
      "rootPatterns": ["elm.json"],
      "initializationOptions": {
        "elmAnalyseTrigger": "change"
      }
    }
  }
}