Go run not searching $GOPATH (SOLVED)

Suddenly my GO system stopped searching $GOPATH for local packages.

I am probably missing something obvious, but I cant see it.

Screen shot attached

Screen shot of minimal code showing problem. I suppose next step is to reload GO

The problem was caused by a file go.mod which appeared in my working directory.

When I compiled another file go.sum also appeared.

I deleted files go.mod and also go.sum and the problem went away.

I screenshot go.mod; maybe someone will recognise it.