Validating Email Addresses with Regular Expressions in Go

This challenge focuses on utilizing regular expressions in Go to validate email addresses. Email validation is a crucial aspect of many applications, ensuring data integrity and preventing errors. Your task is to write a Go function that accurately determines whether a given string conforms to a standard email address format.

Problem Description

You need to create a Go function named IsValidEmail that takes a string as input and returns a boolean value indicating whether the input string is a valid email address according to a reasonable regular expression. A valid email address generally follows the pattern: username@domain.tld, where username can contain alphanumeric characters and some special characters, domain is a domain name, and tld is a top-level domain (e.g., .com, .org, .net).

Key Requirements:

• The function must accept a string as input.
• The function must return true if the input string is a valid email address, and false otherwise.
• The regular expression should be reasonably robust, covering common email address formats. It doesn't need to be perfectly exhaustive (covering every possible valid email), but should handle typical cases well.
• The function should handle empty strings and nil inputs gracefully (returning false).

Expected Behavior:

The function should accurately identify valid and invalid email addresses based on the regular expression. It should not throw any errors.

Edge Cases to Consider:

• Empty strings.
• Strings with only spaces.
• Strings with invalid characters in the username or domain.
• Strings with missing @ symbol.
• Strings with missing domain or TLD.
• Strings with multiple @ symbols.
• Strings with invalid TLDs (e.g., just a single character).

Examples

Example 1:

Input: "test@example.com"
Output: true
Explanation: This is a standard, valid email address.

Example 2:

Input: "invalid-email"
Output: false
Explanation: This string is missing the "@" symbol and domain.

Example 3:

Input: "user.name+alias@sub.example.co.uk"
Output: true
Explanation: This is a valid email address with a subdomain and alias.

Example 4:

Input: ""
Output: false
Explanation: An empty string is not a valid email address.

Example 5:

Input: "  "
Output: false
Explanation: A string containing only spaces is not a valid email address.

Constraints

• The input string will be a string of maximum length 255 characters.
• The function must be implemented in Go.
• The regular expression should be efficient enough to execute within a reasonable time (e.g., less than 10ms for a typical email address).
• The function should not panic or throw any runtime errors.

Notes

• Consider using the regexp package in Go.
• Regular expression syntax can be tricky. Test your expression thoroughly with various valid and invalid email addresses.
• While a perfect email validation regex is extremely complex, aim for a balance between accuracy and readability. Don't try to cover every single edge case.
• Focus on handling common and likely scenarios effectively.
• Remember to handle the nil input gracefully. While the problem description states the input is a string, it's good practice to handle potential nil values. You can treat a nil input as an empty string.