golang-for-devops

```go
package main

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"time"

	"github.com/shirou/gopsutil/v3/disk"
)

// DiskUsageReport represents the structure of the JSON output
type DiskUsageReport struct {
	Timestamp   string  `json:"timestamp"`
	DiskName    string  `json:"disk_name"`
	UsagePercent float64 `json:"usage_percent"`
	Status      string  `json:"status"`
}

func main() {
	// Get disk partitions
	partitions, err := disk.Partitions(false)
	if err != nil {
		log.Fatalf("Failed to get disk partitions: %v", err)
	}

	// Filter for physical disks (exclude tmpfs, etc.)
	var physicalDisks []string
	for _, p := range partitions {
		if p.Fstype != "tmpfs" && p.Fstype != "devtmpfs" {
			physicalDisks = append(physicalDisks, p.Mountpoint)
		}
	}

	// Check usage for each disk
	reports := make([]DiskUsageReport, 0)
	for _, mountpoint := range physicalDisks {
		usage, err := disk.Usage(mountpoint)
		if err != nil {
			log.Printf("Failed to get usage for %s: %v", mountpoint, err)
			continue
		}

		status := "healthy"
		if usage.UsedPercent >= 90 {
			status = "critical"
		} else if usage.UsedPercent >= 80 {
			status = "warning"
		}

		report := DiskUsageReport{
			Timestamp:   time.Now().Format(time.RFC3339),
			DiskName:    mountpoint,
			UsagePercent: usage.UsedPercent,
			Status:      status,
		}
		reports = append(reports, report)

		// Print to console for immediate visibility
		fmt.Printf("Disk %s: %.2f%% used (%s)\n", mountpoint, usage.UsedPercent, status)
	}

	// Write JSON report to file
	jsonData, err := json.MarshalIndent(reports, "", "  ")
	if err != nil {
		log.Fatalf("Failed to marshal JSON: %v", err)
	}

	err = os.WriteFile("/var/log/disk_usage_report.json", jsonData, 0644)
	if err != nil {
		log.Fatalf("Failed to write JSON report: %v", err)
	}

	// Exit with non-zero code if any disk is in critical state
	for _, r := range reports {
		if r.Status == "critical" {
			os.Exit(1)
		}
	}
}
```

### Example Output (JSON Report):
```json
[
  {
    "timestamp": "2023-11-15T14:30:45Z",
    "disk_name": "/",
    "usage_percent": 78.5,
    "status": "warning"
  },
  {
    "timestamp": "2023-11-15T14:30:45Z",
    "disk_name": "/var",
    "usage_percent": 92.3,
    "status": "critical"
  },
  {
    "timestamp": "2023-11-15T14:30:45Z",
    "disk_name": "/home",
    "usage_percent": 45.2,
    "status": "healthy"
  }
]
```

Console Output:
```
Disk /: 78.50% used (warning)
Disk /var: 92.30% used (critical)
Disk /home: 45.20% used (healthy)
```