Go Regex Validator: Email Address Checker

This challenge focuses on practical application of Go's regexp package to validate data. You will be tasked with creating a robust email address validator using regular expressions in Go. This skill is fundamental for data sanitation and user input validation in many applications.

Problem Description

Your goal is to write a Go function that takes a string as input and returns true if the string is a valid email address, and false otherwise. You must use Go's built-in regexp package to achieve this validation.

Key Requirements:

1. Email Validation Logic: Implement a regular expression that adheres to common email address formats. A valid email address generally consists of a local part, an "@" symbol, and a domain part.
   • Local Part: Can contain alphanumeric characters, periods (.), hyphens (-), and plus signs (+). It cannot start or end with a period. Consecutive periods are not allowed.
   • Domain Part: Consists of one or more labels separated by periods. Each label can contain alphanumeric characters and hyphens. Labels cannot start or end with a hyphen. The top-level domain (TLD) must be at least two characters long and consist of letters only.
2. Go regexp Package Usage: You must use the regexp package for matching.
3. Function Signature: The function should have the signature func IsValidEmail(email string) bool.
4. Case Insensitivity: The validation should be case-insensitive.

Expected Behavior:

The function should accurately identify valid and invalid email addresses according to the specified criteria.

Edge Cases to Consider:

• Empty strings.
• Strings with leading/trailing whitespace.
• Emails with unusual but technically valid characters (e.g., + in the local part).
• Emails with invalid domain structures (e.g., no TLD, invalid characters in TLD).
• Emails with consecutive dots or dots at the start/end of the local part.

Examples

Example 1:

Input: "test.email+alias@example.com" Output: true Explanation: This is a valid email address. The local part "test.email+alias" is valid, and the domain "example.com" is valid with a TLD "com".

Example 2:

Input: "invalid-email@domain" Output: false Explanation: This is an invalid email address because the domain part is missing a top-level domain (e.g., ".com", ".org").

Example 3:

Input: "another..email@domain.co.uk" Output: false Explanation: This is an invalid email address because the local part contains consecutive periods.

Example 4:

Input: " leading.space@domain.com" Output: false Explanation: This is an invalid email address due to leading whitespace. (Note: If you decide to trim whitespace before validation, this would be true. The problem statement implies exact string matching for validity unless specified otherwise, but consider this as a point for discussion).

Example 5:

Input: "user@domain-.com" Output: false Explanation: This is an invalid email address because the domain label ends with a hyphen.

Constraints

• The input email string will be at most 254 characters long.
• The input email string will consist of printable ASCII characters.
• The regular expression should be compiled once for efficiency if the function is called multiple times.

Notes

• While there are many RFC specifications for email addresses, this challenge focuses on a common, practical subset of valid formats. Aim for a regex that covers most everyday email addresses.
• Consider how to handle potential errors during regex compilation (though for this challenge, you can assume the regex will be valid).
• Think about the order of operations: Should you trim whitespace before applying the regex? The problem description implies strict validation of the input string as-is.
• A good starting point for a regex might involve capturing the local part, the "@" symbol, and the domain part separately.