Consider such situation. There are one main goroutine and ten subsidiary
goroutines. All of them have access to channel. Main one sends 1000 numbers to this channel and subsidiary ones will read from it.
Is there any guarantee that each subsidiary goroutine will read exactly 100 numbers or this amount may vary like some goroutine will read 99 numbers and another 101?
No, there is no guarantee, because it depends on the runtime of every goroutine and that depends on how well the goroutines are distributed across the CPU.