Infinite loops in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple infinite loop with break

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
  i := 0
  for {
    if i == 3 {
      break
    }
    fmt.Print(i)
    i++
  }
}

A 123

B 0123

C 012

D 0

💡 Hint

Look at when the loop stops printing.

The loop prints i starting from 0. When i reaches 3, the break stops the loop before printing 3.

❓ Predict Output

intermediate

Output of infinite loop with continue

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
  i := 0
  for {
    i++
    if i%2 == 0 {
      continue
    }
    if i > 5 {
      break
    }
    fmt.Print(i)
  }
}

A 1357

B 12345

C 246

D 135

💡 Hint

Only odd numbers less than or equal to 5 are printed.

The loop increments i, skips even numbers with continue, prints odd numbers, and stops when i > 5.

🔧 Debug

advanced

Identify the cause of infinite loop

Why does this Go program run forever without stopping?

Go

package main
import "fmt"
func main() {
  i := 0
  for i < 5 {
    fmt.Print(i)
  }
}

A Variable i is never incremented inside the loop

B The loop condition is always false

C The fmt.Print causes the loop to restart

D The for loop syntax is invalid

💡 Hint

Check if the loop variable changes inside the loop.

The variable i stays 0 forever, so the condition i < 5 is always true, causing an infinite loop.

📝 Syntax

advanced

Which option causes a compile error due to infinite loop syntax?

Which of these Go loop statements will cause a compile error?

A for i := 0; i < 5 {}

B for i := 0; i < 5; i++ {}

C for {}

D for i := 0; i < 5; i++ { break }

💡 Hint

Check if the for loop header has all three parts separated by semicolons.

Option A misses the increment part after the second semicolon, causing a syntax error.

🚀 Application

expert

How many times does this infinite loop print?

How many times will the following Go program print "Hello" before stopping?

Go

package main
import "fmt"
func main() {
  count := 0
  for {
    fmt.Println("Hello")
    count++
    if count == 10 {
      break
    }
  }
}

A 9

B 10

C Infinite times

D 0

💡 Hint

Look at how count changes and when the break happens.

The loop prints "Hello" and increments count each time. When count reaches 10, it breaks.

Practice

1. What does the following Go code do?

for { }

easy

A. Runs an infinite loop that never stops

B. Runs a loop 10 times

C. Runs a loop only once

D. Causes a syntax error

Solution

1. Step 1: Understand the loop syntax

   The code uses for { } which is Go's way to write an infinite loop without conditions.

2. Step 2: Analyze loop behavior

   Since there is no break or condition, the loop runs forever without stopping.

3. Final Answer:

   Runs an infinite loop that never stops -> Option A

4. Quick Check:

   for { } means infinite loop [OK]

Hint: for { } always means infinite loop in Go [OK]

Common Mistakes:

• Thinking it runs a fixed number of times
• Assuming it causes a syntax error
• Confusing with loops that have conditions

2. Which of the following is the correct syntax for an infinite loop in Go?

easy

A. for i := 0; i < 10; i++ { }

B. loop forever { }

C. for { }

D. while true { }

Solution

1. Step 1: Review Go loop syntax

   Go does not have a while or loop keyword; infinite loops use for { }.

2. Step 2: Identify correct infinite loop

   for { } uses for { }, which is the correct infinite loop syntax in Go.

3. Final Answer:

   for { } -> Option C

4. Quick Check:

   Go infinite loop syntax = for { } [OK]

Hint: Remember: Go uses for { } for infinite loops [OK]

Common Mistakes:

• Using while or loop keywords (not in Go)
• Confusing for loops with conditions as infinite
• Syntax errors from invalid keywords

3. What will be the output of this Go program?

package main
import "fmt"
func main() {
  count := 0
  for {
    if count == 3 {
      break
    }
    fmt.Println(count)
    count++
  }
}

medium

A. 0 1 2

B. 0 1 2 3

C. Infinite printing of numbers

D. No output

Solution

1. Step 1: Understand loop and break condition

   The loop runs infinitely but breaks when count equals 3.

2. Step 2: Trace output values

   It prints count values 0, 1, 2 then breaks before printing 3.

3. Final Answer:

   0 1 2 -> Option A

4. Quick Check:

   Loop breaks at count==3, prints 0 to 2 [OK]

Hint: Break stops infinite loop at condition [OK]

Common Mistakes:

• Expecting 3 to be printed
• Thinking loop runs forever
• Ignoring break statement

4. Identify the problem in this Go code that causes an infinite loop and fix it:

package main
import "fmt"
func main() {
  i := 0
  for i < 5 {
    fmt.Println(i)
  }
}

medium

A. Add break statement without increment

B. Change for to for { }

C. Remove the loop entirely

D. Add i++ inside the loop to increment i

Solution

1. Step 1: Identify loop condition and variable

   The loop runs while i < 5 but i is never changed inside the loop.

2. Step 2: Fix infinite loop by incrementing i

   Adding i++ inside the loop updates i, allowing the loop to end.

3. Final Answer:

   Add i++ inside the loop to increment i -> Option D

4. Quick Check:

   Increment loop variable to avoid infinite loop [OK]

Hint: Always update loop variable to prevent infinite loops [OK]

Common Mistakes:

• Forgetting to increment loop variable
• Adding break without changing i causes infinite loop
• Changing loop to infinite loop syntax accidentally

5. How can you safely implement an infinite loop in Go that stops after 5 seconds?

hard

A. Use for i := 0; i < 5; i++ { }

B. Use for { } with time.After and break when 5 seconds pass

C. Use while true with a timer

D. Use for { } without any break or condition

Solution

1. Step 1: Understand infinite loop with timeout

   Use for { } for infinite loop and time.After to wait 5 seconds.

2. Step 2: Break loop after 5 seconds

   Inside loop, check if 5 seconds passed and use break to stop loop safely.

3. Final Answer:

   Use for { } with time.After and break when 5 seconds pass -> Option B

4. Quick Check:

   Infinite loop + timer + break = safe stop [OK]

Hint: Combine for { } with timer and break to stop [OK]

Common Mistakes:

• Using invalid while syntax
• Not breaking loop causes infinite run
• Using fixed count loop instead of infinite