Tell me about the garbage collector in Go (three-color marking).

Go uses a tri-color marking scheme for implementing a garbage collector (GC) based on the mark-and-sweep algorithm. The main idea is to divide objects into three categories (colors) during graph traversal:

• White: objects that have not been visited yet and may potentially be removed.
• Gray: objects that have been found, but their children have not yet been processed.
• Black: objects that have been visited, and all their children have also been processed.

The algorithm works as follows:

1. All objects are initially white.
2. Root objects (e.g., global variables, stacks) are marked gray.
3. While there are gray objects, take one, mark it black, and mark all its child objects gray (if they are white).
4. After traversal, all white objects are considered unreachable and are removed.

This approach allows for safe and efficient garbage collection without blocking the entire program execution and minimizes pauses. In Go, the garbage collector runs concurrently with the program, using this marking scheme to track live objects.