Fixed Critical Error Handling Issues in main.go

[VedantAnand17]

📋 Summary

This PR addresses critical error handling vulnerabilities in the main application that could cause runtime failures, resource leaks, and poor user experience. All previously ignored errors now have proper handling with appropriate logging and resource cleanup.

🔧 Changes Made

1. File Operations Error Handling

Before:

dataFile, _ := os.Open("./data.json")
byteRes, _ := io.ReadAll(dataFile)
json.Unmarshal([]byte(byteRes), &data)
defer dataFile.Close()

After:

dataFile, err := os.Open("./data.json")
if err != nil {
    log.Fatalf("Failed to open data.json: %v", err)
}
defer dataFile.Close()

byteRes, err := io.ReadAll(dataFile)
if err != nil {
    log.Fatalf("Failed to read data.json: %v", err)
}

err = json.Unmarshal([]byte(byteRes), &data)
if err != nil {
    log.Fatalf("Failed to parse data.json: %v", err)
}

2. Template Parsing Error Handling

Before:

table, _ := template.ParseFiles("./templates/table.html")
home, _ := template.ParseFiles("./templates/home.html")
courseNameCode, _ := template.ParseFiles("./templates/course-name-code.html")
errorPage, _ := template.ParseFiles("./templates/error.html")

After:

table, err := template.ParseFiles("./templates/table.html")
if err != nil {
    log.Fatalf("Failed to parse table template: %v", err)
}

home, err := template.ParseFiles("./templates/home.html")
if err != nil {
    log.Fatalf("Failed to parse home template: %v", err)
}

courseNameCode, err := template.ParseFiles("./templates/course-name-code.html")
if err != nil {
    log.Fatalf("Failed to parse course-name-code template: %v", err)
}

errorPage, err := template.ParseFiles("./templates/error.html")
if err != nil {
    log.Fatalf("Failed to parse error template: %v", err)
}

3. HTTP Handler Error Handling

Before:

errorPage.Execute(w, "This page is under construction !!(404)")
table.Execute(w, data)
courseNameCode.Execute(w, h)

After:

if err := errorPage.Execute(w, "This page is under construction !!(404)"); err != nil {
    log.Printf("Error while executing error template: %v", err)
}

if err := table.Execute(w, data); err != nil {
    log.Printf("Error while executing table template: %v", err)
}

if err := courseNameCode.Execute(w, h); err != nil {
    log.Printf("Error while executing course template: %v", err)
}

🎯 Issues Fixed

Critical Issues

• Resource Leaks: File handles now properly closed with defer statement
• Silent Failures: All ignored errors now properly handled and logged
• Runtime Crashes: Template parsing errors now cause graceful startup failures
• Poor Error Reporting: Clear error messages for debugging

Security & Reliability

• Startup Validation: Server fails fast with clear messages if critical files are missing
• Graceful Degradation: Template execution errors logged without crashing the server
• Proper Resource Management: Guaranteed cleanup of file handles

🧪 Testing

Manual Testing Scenarios

1. Missing data.json: Server should fail to start with clear error message
2. Corrupted data.json: Server should fail to start with JSON parsing error
3. Missing template files: Server should fail to start with template parsing error
4. Template execution errors: Should log error but continue serving other requests

Expected Behavior

• Server startup fails immediately if critical resources are missing
• Runtime template errors are logged but don't crash the server
• All file handles are properly closed
• Clear error messages for debugging

📊 Impact

Positive Impact

• ✅ Improved Reliability: Server won't silently fail on missing files
• ✅ Better Debugging: Clear error messages for troubleshooting
• ✅ Resource Safety: No more potential file handle leaks
• ✅ Production Ready: Proper error handling for deployment

Risk Assessment

• Low Risk: Changes only add error checking, no functional changes
• Backward Compatible: No breaking changes to existing functionality
• Performance: Minimal overhead from error checking

🔍 Code Review Checklist

• All file operations have proper error handling
• Template parsing errors are handled at startup
• HTTP handler errors are logged but don't crash server
• Resource cleanup is guaranteed with defer statements
• Error messages are descriptive and actionable
• No functional changes to existing behavior
• Code follows Go error handling best practices

📝 Related Issues

• Addresses critical error handling vulnerabilities
• Improves production readiness
• Enhances debugging capabilities

🚀 Deployment Notes

• No special deployment considerations
• Changes are backward compatible
• Monitor logs for any new error messages during deployment

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Type: Bug Fix
Priority: Critical
Breaking Changes: None
Testing Required: Manual testing of error scenarios