This "ToDo" is one of the sample projects detailed in the book "ExtJS by Example". This sample application uses ExtJS 6 and GoLang. To run this sample application, simply clone or download, and run the following command in terminal window and open localhost:9001 in the browser.
go run server/ToDO.go
Note, this example uses cloudflare CDN for ExtJS 6. If the CDN doesn't work, you may need to update ExtJS lib urls in index.html and point to the local ExtJS library path.
The installation guide for ExtJS 6, Sencha Cmd, GoLang are explained in the book "ExtJS by Example".