goInfinite loopMedium

Deadlock in range loop over unclosed channel

Time: 0:00

BugFind the bug and fix the code

What it should do

Drain all queued integers from a channel into a slice. Example: drainTaskQueue(3) -> [1, 2, 3]

What happens instead

fatal error: all goroutines are asleep - deadlock!

package main

import "fmt"

func drainTaskQueue(n int) []int {
	ch := make(chan int, n)
	for i := 1; i <= n; i++ {
		ch <- i
	}
	var res []int
	for val := range ch {
		res = append(res, val)
	}
	return res
}

func main() {
	fmt.Println(drainTaskQueue(3))
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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Hints

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Hint 2

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Hint 3

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This bug belongs to the infinite loops pattern

The tab freezes, nothing prints, and the loop condition never becomes false.

Learn the infinite loops pattern Step through your own code

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package main import "fmt" func drainTaskQueue(n int) []int { ch := make(chan int, n) for i := 1; i <= n; i++ { ch <- i } var res []int for val := range ch { res = append(res, val) } return res } func main() { fmt.Println(drainTaskQueue(3)) }

Deadlock in range loop over unclosed channel

What it should do

What happens instead

More infinite loops to practise

Seen this error in your own code?

Deadlock in range loop over unclosed channel

What it should do

What happens instead

More infinite loops to practise

Seen this error in your own code?