How to shift user input in C (console, multithreading)?

Question

Command line

In simple terms: there are two threads, one leaves messages, the second waits for user input in the same console. How to make the user input line shift when a message arrives.

Answer 1

Protect console output with a mutex: grab it before printing lines to the screen from the second stream and release it immediately after.
When a character appears in the keyboard buffer (_kbhit() became true):

1. Grab the mutex
2. output tabs or lots of spaces
3. read string by any library function
4. release the mutex