Welcome to the first lesson of this course where we'll practice the fundamentals of string manipulation in Go, specifically focusing on scenarios where we refrain from using built-in string methods. Navigating complex character strings is an integral part of a software developer's toolkit, and Go provides essential features to manage and manipulate strings effectively. Nevertheless, to truly master your craft, it's critical to peel back the layers and understand the core principles that power these built-in methods. This understanding will not only establish a stronger foundation in the language but also equip you to handle situations where you might not have the luxury of using these high-level functions or where custom solutions would be more efficient.

In Go, strings are essentially sequences of bytes, often used to represent text. Strings in Go are immutable, meaning once a string is created, it cannot be changed. This is different from some other languages where strings can be modified directly. Instead, string manipulations often involve creating new strings from existing ones.

Since Go strings are immutable, any "modification" to a string results in the creation of a new string. To facilitate manual manipulation, we rely on converting strings to slices of runes or bytes, allowing easier handling of individual characters, especially considering Unicode support.

Basic operations for manually manipulating strings include:

• Accessing characters using indexing after converting to a slice of runes or bytes.
• Building strings using the strings.Builder or direct concatenation.
• Using len() to get the length of the string in bytes, or converting it to a slice of runes for character length.

Understanding these principles will empower you to perform fundamental string manipulations without relying on Go’s higher-level built-in methods.

Consider a simple operation such as reversing a string. We could use built-in functions from the strings package, but the task requires that we do not use built-in functions.

Our approach to this challenge is:

1. Convert String to Rune Slice: Convert the string to a slice of runes to properly handle Unicode characters.

2. Set Up a Loop: Utilize a loop to traverse the rune slice from the last element to the first element.

3. Append Characters in Reverse Order: Within the loop, append the rune at the current index to a new slice.

4. Convert the Rune Slice Back to a String: Once you’ve reversed the rune slice, convert it back to a string.

5. Return the Reversed String: Return the new string that now contains the characters of the original string in reverse order.

Here is how the solution will look:

Take your time to digest this concept since it forms the basis of more elaborate tasks that we will encounter later. Once you're ready, let's dive into some hands-on programming exercises that will give you a practical feel for these concepts. Remember, our goal isn't simply to memorize algorithms but to develop an understanding of how to systematically break down and address problems — a skill that is at the heart of programming. As always, practice is your best friend, so let's get coding!