https://blog.canopas.com/golang-interacting-with-google-spreadsheets-b381f819c2eb - update-cell

update-cell.go

// https://docs.google.com/spreadsheets/d/<SPREADSHEETID>/edit#gid=<SHEETID>
spreadsheetId := <SPREADSHEETID>

// The A1 notation of cells range to update.
range2 := "A1:C1" 

// prepare data for update cells
row := &sheets.ValueRange{
	Values: [][]interface{}{{"2", "XYZ", "[email protected]"}},
}

// update cells in given range 
_, err = srv.Spreadsheets.Values.Update(spreadsheetId, range2, row).ValueInputOption("USER_ENTERED").Context(ctx).Do()
if err != nil {
	log.Fatal(err)
}