How does mutex work in a buffered channel? What does it protect?

In Go, a buffered channel contains an internal buffer of fixed size, which stores elements sent to the channel but not yet received. To ensure proper access to this buffer, a mutex (mutual exclusion) is used.

The mutex protects the internal data structures of the channel from concurrent access by multiple goroutines. This guarantees that send and receive operations are atomic and do not lead to race conditions.

In other words, the mutex ensures:

• Consistency of the buffer state (read and write indices, number of elements).
• Safety during concurrent send and receive operations.
• Proper locking and unlocking of goroutines when filling or emptying the buffer.

Thus, the mutex in a buffered channel protects the internal buffer and its associated metadata from concurrent modifications, ensuring correct synchronization between goroutines.