I have been getting this error message a lot, and I get sent to this documentation page. I am not editing anything in an external editor.
Also, the cursor sometimes jumps around inexplicably, particularly as I do auto-suggest (command-Space). (Note that I use IdeaVIM)
My guess is that File Watchers are involved (gocmt, gofmt, goimport, golint). These are triggered on save (which happens automatically) and some potentially edit a fie immediately, so that the save can conflict with the File Watcher's action. But I have no good evidence for that guess.
How can I avoid this?
What can I do about this?