To watch and observe a Google Sheet in GoLang, you can use the Google Sheets API to access the sheet and the time package to set up a timer to check for changes periodically. Here's an example code snippet that demonstrates this:

main.go

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"google.golang.org/api/sheets/v4"
	"google.golang.org/api/option"
)

func main() {
	// Set up the Google Sheets API client.
	ctx := context.Background()
	creds, err := google.FindDefaultCredentials(ctx, sheets.Scope)
	if err != nil {
		log.Fatalf("Unable to retrieve credentials: %v", err)
	}
	client, err := google.DefaultClient(ctx, sheets.Scope, option.WithCredentials(creds))
	if err != nil {
		log.Fatalf("Unable to create Google Sheets API client: %v", err)
	}
	sheetsService, err := sheets.New(client)
	if err != nil {
		log.Fatalf("Unable to create Google Sheets API service: %v", err)
	}

	// Specify the spreadsheet ID and sheet range.
	spreadsheetID := "<your spreadsheet ID>"
	sheetRange := "<your sheet name>"

	// Set up a timer to check for changes every 5 seconds.
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	// Loop indefinitely to watch for changes.
	for {
		select {
		case <-ticker.C:
			// Call the Google Sheets API to get the latest data from the sheet.
			resp, err := sheetsService.Spreadsheets.Values.Get(spreadsheetID, sheetRange).Do()
			if err != nil {
				log.Fatalf("Unable to retrieve data from sheet: %v", err)
			}

			// Print the data to the console.
			fmt.Printf("Data: %v\n", resp.Values)
		}
	}
}